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Group Title: Hydrobiid snail genus Marstonia (FLMNH Bulletin v.21, no.3)
Title: The Hydrobiid snail genus Marstonia
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00095840/00001
 Material Information
Title: The Hydrobiid snail genus Marstonia
Physical Description: p. 113-158 : ill. ; 23 cm.
Language: English
Creator: Thompson, Fred G ( Fred Gilbert ), 1934-
Donor: unknown ( endowment )
Publisher: Florida State Museum, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1977
Copyright Date: 1977
 Subjects
Subject: Marstonia -- Classification   ( lcsh )
Mollusks -- Classification   ( lcsh )
Mollusks -- Southern States   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 131-132.
General Note: Bulletin of the Florida State Museum, Biological sciences, volume 21, number 3
Statement of Responsibility: Fred G. Thompson.
 Record Information
Bibliographic ID: UF00095840
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 03887109
lccn - 78621450

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Full Text









of the
FLORIDA STATE MUSEUM
Biological Sciences


1977


Number 3


THE HYDROBIID SNAIL GENUS MARSTONIA


FRED G. THOMPSON


UNIVERSITY OF FLORIDA


Volume 21


GAINESVILLE









Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM, BIOLOGICAL SCIENCES,
are published at irregular intervals. Volumes contain about 300 pages and are not necessarily
completed in any one calendar year.










CARTER R. GILBERT, Editor
RHODA J. RYBAK, Managing Editor

Consultants for this issue:

JOHN B. BURCH
















Communications concerning purchase or exchange of the publications and all manuscripts
should be addressed to the Managing Editor of the Bulletin, Florida State Museum, Museum
Road, University of Florida, Gainesville, Florida 32611.


Publication date: January 21, 1977


This public document was promulgated at an annual cost of $1,705.74 or
$1.705 per copy. It makes available to libraries, scholars, and all interested
persons the results of researches in the natural sciences, emphasizing the
Circum-Caribbean region.


Price $1.75

































THE HYDROBIID SNAIL GENUS MARSTONIA


FRED G. THOMPSON'


SYNOPSIS: The recent species of Marstonia are revised, based on material in most major mu-
seum collections and on new material recently collected in the southeastern states. A total of
eight species are recognized, of which five are described as new: M. arga, M. ogmnorhapha, and
M. pachyta from the Tennessee River system; M. castor from the Flint River system, Georgia;
and M. halcyon from the Ogeechee River system, Georgia. Five names are placed in the syn-
onymy of Marstonia lustrica (Pilsbry): Amnicola oneida Pilsbry, A. winkleyi Pilsbry, A. perlus-
trica Baker, M. decepta Baker, and M. gelida Baker. M. olivacea is considered a distinct species
of uncertain status and is probably extinct. Marstonia is placed in the subfamily Nymphophilinae
and is most closely related to Cincinnatia. Other North American genera in Nymphophilinae
include Fonticella, Notogillia, Spilochlamys, Rhapinema, Nymphophila, and Birgella.














' The author is Associate Curator in Malacology at the Florida State Museum and Associate Professor in the Department of
Zoology, University of Florida, Gainesville 3261T. Manuscript accepted 3 August 1975.


Thompson, Fred G. 1977. The Hydrobiid Snail Genus Marstonia. Bull. Florida State Mus., Biol.
Sci., Vol. 21, No. 3, pp. 113-158.






114 BULLETIN FLORIDA STATE MUSEUM Vol. 21, No. 3

TABLE OF CONTENTS

IN T R O D U C T IO N .................................................................................................. .......................... 1 14
A C KN O W LE D G M E N T S .... ........................................................................................................ ...... 115
M arstonia F C BAKER 1926 ............................ ................................................ ...... ... 115
SPECIES OF Q UESTIONABLE STATUS .............................................................................................. 118
K EY TO THE SPECIES OF M arstonia .............................................................................................. 118
M arstonia arga new species ................................................. ............................................... 119
M arstonia ogm orhapha new species ......................................... ......................................... 120
M arstonia pachyta new species .............................................. ............................................ 121
M arstonia olivacea (P ILSBRY) ............................... ....................................................................... 122
M arstonia lustrica (P ILSBRY .......................................................................................................... 124
M arstonia halcyon new species ........................................................ ........................................ 128
M arstonia castor new species............................... ..................................................................... 130
M arstonia agarhecta T HOM PSON .................................................................................................. 130
L IT E RA T U R E C IT E D ................................................... ......................... .......................................... 13 1
F IG U R E S .......................................................................................................................................... 1 3 3



INTRODUCTION

Attempts to define many genera and species of southeastern hydrobiid
snails necessitates restudy of taxa long known from the north-central United
States. A genus of particular note is Marstonia and its wide-ranging cold-
temperate species M. lustrica (Pilsbry). Even though the species is widely dis-
tributed throughout the Great Lakes region and has been known since 1890,
there exists a dearth of information on its eco-geographic variation and
anatomy. All previous studies on geographic variation were confined to single
states, and anatomical observations have been limited to the verge of the male.
The discovery of several undescribed species of Marstonia in the Tennessee,
Flint, Ocmulgee, and Ogeechee river systems necessitates a review of all other
known taxa referable to the genus. Anatomical data provide a basis for re-
lating Marstonia to other North American genera with a lobed verge, and to
similar European genera about which a great deal of anatomical information
is available, particularly through the studies of P. Radoman and H. D. Boeters
(see references). The following study does not pretend to be definitive. Some
species from the Tennessee and Coosa rivers are left undescribed because
anatomical specimens of these forms are not available. Also, additional spe-
cies can be anticipated in other river systems.
Marstonia was regarded as a subgenus of Amnicola until recently (Taylor
1960:51), as were other distinct groups of hydrobiid snails that possess small,
simple, conical shells. All specific and subspecific forms of Marstonia de-
scribed prior to 1969 were named as species of Amnicola. Morrison (1949:13-
15) demonstrated that Amnicola and Marstonia belong to different subfamilies
(see Thompson 1968:147-167). Marstonia currently is placed in the subfamily
Nymphophilinae Taylor 1966.







THOMPSON: SNAIL GENUS MARSTONIA


When F. C. Baker (1926:195) proposed Marstonia as a subgenus of Amni-
cola, he included seven species: Amnicola lustrica Pilsbry, A. gelida F. D.
Baker, A. oneida Pilsbry, A. walker Pilsbry, A. pilsbryi Walker, A. greenensis
F. C. Baker, and A. winkleyi Pilsbry. Of these, A. walker and A. pilsbryi are
species of Lyogyrus (Thompson 1968:162-163); and A. oneida, A. gelida, and
A. winkleyi are here considered objective secondary synonyms of M. lustrica.
A. greenensis is a Pleistocene fossil. Speculation about its generic affinities
is fruitless, because critical anatomical data are not available for such fossil
species. Taylor (1960:50) placed the Pliocene Amnicola crybetes Leonard
1952 in Marstonia, but that allocation is also purely speculative. Thus, M.
lustrica was the only species unequivocably placed in Marstonia until recently
when M. agarhecta was described (Thompson 1969:242-247).

ACKNOWLEDGMENTS
Many people have assisted me in this study. To all of them I am grateful for their contribu-
tions in time and thought. For the loan of specimens in their charges I wish to acknowledge:
Kenneth J. Boss, Museum of Comparative Zoology (MCZ); Joseph Rosewater and Joseph P. E.
Morrison, United States National Museum of Natural History (USNM); J. B. Burch and Henry
van der Schalie, Museum of Zoology, University of Michigan (UMMZ); Juan Jose Parodiz,
Carnegie Museum (CM); Alan Solem, Field Museum of Natural History (FMNH); and George
M. Davis, Academy of Natural Sciences, Philadelphia (ANSP). Harold J. Walter, Dayton, Ohio,
provided me with critical anatomical material of M. lustrica. Beverly E. Johnson, Gainesville,
Florida, assisted me in fieldwork in Alabama, Georgia, and Tennessee. Figures 1, 2, and 3A-C
were made by Donna Born Drake and the remaining figures by Nancy Halliday; I am grateful
to both for their skillful contributions. The SEM were made by Sylvia Scudder, Florida State
Museum.
Field work in the southern states was supported by funds from three agencies: U. S. Depart-
ment of the Interior, Office of Endangered Species (Contract # 14-16-008-785, 1973), Tennessee
Valley Authority (Contract # TV-37778A, 1973), and the University of Florida, Division of Spon-
sored Research (NIH Biomedical Grant 69-25).

Marstonia F. C. BAKER 1926
Marstonia F. C. Baker 1926:195. (Type species: Amnicola lustrica Pilsbry 1890; see Berry
1943:29, Thompson 1969:242-243.
GENERIC CHARACTERISTICS.-This is a genus of small conical or elliptical-
conical snails, in which the shell seldom exceeds 5 mm. The shell, operculum,
and radula are not diagnostic at the generic level.
The shell is conical to elliptical-conical in shape, with about five whorls at maturity, and is
about 0.46-0.80 times as wide as high. The periostracum is light gray. The peristome is usually
complete across the parietal margin of the aperture, but occasionally it may be incomplete.
Sculpturing either is absent or consists of fine incremental striations. The umbilicus may be
broadly perforate or closed. The embryonic whorls protrude, with the nuclear whorl about
0.25 mm in diameter perpendicular to the initial suture. The embryonic sculpture consists of a
densely folded and anastomosing series of wrinkles and pits, and is similar to that found in other
bilobed American hydrobiid genera (Fig. 4).
The operculum (Fig. 25) is paucispiral, thin, membranous, transparent, ovate to modified
elliptical in outline, and consists of about 2.5 whorls. The nucleus is near the left and lower third

of the outer face. The radula is taenioglossate with the following formula: C3T--5,







BULLETIN FLORIDA STATE MUSEUM


L(2-4)-1-(3-5) M's (15-20). The basocones rise from the lateral angle of the tooth. The stomach
lacks a tube-shaped caecal appendage on the esophageal end.
The foot is broadly rounded posteriorly and truncate anteriorly. It moves over the substrate
by a gliding ciliary movement. A deep mucous slit overlies the anterior margin. A suprapedal
fold and an external omniphoric fold are absent. A short, weak fold underlies the anterior half
of the operculigerous lobe on each side. The eyes lie at the base of the tentacles and are raised.
The snout, foot, and nape may be pigmented to varying degrees with melanin. Usually the
mantle bears two diffuse black stripes over the mantle cavity. One stripe overlies or parallels
the left margin of the intestine, and the other overlies or parallels the left margin of the gill. The
two bands usually unite over the pericardium. Occasionally the bands are broader and almost
completely cover the mantle cavity and the posterior viscera. The central nervous system is un-
pigmented.
The male reproductive system of M. lustrica is illustrated in Figure 5A. The verge originates
on the nape beneath the mantle, just to the right of the middorsal line, and is innervated by the
right pleural ganglion. The verge is bilobed distally, and bears a large apical lobe, a short
terminal penis, and a single duct, the vas deferens. The apical lobe bears a single enlarged apical
gland, although some species have an additional smaller gland near the base of the verge. The
glands are apocrine. The gonad consists of 3-5 large lobes. The vas deferens I is strongly con-
voluted near its middle, at which point the vas wall is thickened and glandular. The prostate is
fan-shaped or reniform and overlaps the posterior end of the mantle cavity. The vas deferens HI
is simple and is a closed duct from the prostate to the tip of the penis. A diverticulum to the
mantle cavity is absent from either the vas deferens I or II.
The female reproductive system of M. lustrica is illustrated in Figures 6B, C. The ovary con-
sists of three primary lobes, each of which may be divided into 2-4 secondary lobes. Each lobe
is the diameter of one primary oocyte. The oviduct I is relatively short and thick, becoming nar-
rower anteriorly. Just posterior to the wall of the mantle cavity the oviduct forms a large in-
verted U-shaped loop along, and transverse to, the middle of the posterior section of the pallial
oviduct. The wall of the loop along this U-segment is very thick and glandular. (This glandular
loop may serve as an albumen gland.) The single seminal receptacle is small, saculate, lies along
the ventral margin of the posterior pallial oviduct, and enters the end of the oviduct loop by a
very short duct. The seminal receptacle is homologous to the seminal receptacle 2 of Radoman
(1973). The bursa copulatrix overlies the posterior mesad surface of the posterior pallial oviduct.
It has a relatively long duct that is usually imbedded in the latter structure. The bursal duct
enters the oviduct I just posterior to the anterior pallial oviduct. A short gonopericardial duct
(GPD) connects the oviduct I to the pericardium. Neither a receptacular duct nor a bursal duct
(which would connect either of these structures to the posterior mantle cavity) is present. The
oviduct II is closed within the anterior pallial oviduct. The female opening is a short vaginal
slit. A short omniphoric groove connects the vaginal slit to the anterior margin of the mantle
collar.
GEOGRAPHIC DisTRIBUTrrION.-Marstonia is widely distributed in eastern North America, al-
though it does not have a continuous range in that area. One species, M. lustrica, occurs through-
out the St. Lawrence River system, the Great Lakes region, and the upper Mississippi River
system. A disjunct group of species is found in the Tennessee River system in northern Alabama
and adjacent Tennessee and in the Coosa River of Alabama. Three isolated species occur in the
Flint, Ocmulgee, and Ogeechee river systems in Georgia. Marstonia probably occurs in other
rivers in Georgia and Alabama.
The present distribution of Marstonia strongly suggests that the genus originated in the Ten-
nessee River system and dispersed from there. This interpretation is based on the species diver-
sity presently existing in the Tennessee River. The species there comprise a natural group, from
which the more northern species, M. lustrica, presumably was derived during the Wisconsin
Glacial Period. A second lineage invaded the coastal drainages of Georgia, probably via the
Savannah River System, and evolved as a strongly differentiated species group. The time at which
the coastal invasion occurred is not clear, but it probably was during the Pliocene or very early
Pleistocene.
RELATIONSHIPS.-Marstonia, as is true of other hydrobine snails, has a
single duct (the vas deferens) within the male reproductive appendage. The
genus belongs to a group that also includes the North American Nymphophila


Vol. 21, No. 3






THOMPSON: SNAIL GENUS MARSTONIA


Taylor 1966, Cincinnatia Pilsbry 1891, Fontelicella Gregg and Taylor 1965,
Birgella F. C. Baker 1926, Rhapinema Thompson 1969, Notogillia Pilsbry
1953, Spilochlamys Thompson 1968, and perhaps Pyrgulopsis Call and Pilsbry
1886. The reproductive anatomies of these genera remain unstudied except
for the verge. I examined internally males of all but Fontelicella and Pyrgulop-
sis. The males are alike in having (1) a bilobed verge with a slender terminal
penis off the right margin; (2) a single duct, the vas deferens, within the verge;
(3) various superficial apocrine glands on the verge, apical crest, and/or
penis; (4) the verge innervated by the right pleural ganglion; and (5) a con-
nective absent between the vas deferens and the mantle cavity. I have ex-
amined cursorily the female reproductive systems of Notogillia, SpilochlainIs,
Rhapinema, Cincinnatia, and Birgella, and find they are basically similar to
Marstonia. The females of these genera agree in having (1) a thick, glandular-
walled loop in the oviduct I beside, and mesad to, the posterior pallial oviduct;
(2) a gonopericardial duct; (3) a single seminal receptacle (SR 2) at the base of
the oviduct loop; (4) a bursa copulatrix that has a duct partially imbedded in
the posterior pallial oviduct; and (5) a closed oviduct II within the anterior
pallial oviduct.
The oldest and only group name proposed for the North American bi-
lobed-verge genera is the Nymphophilinae Taylor 1966. Other North Ameri-
can hydrobine genera have an unlobed verge and are placed in different sub-
families. These other genera remain unstudied internally and further com-
ments on similarities or differences are not possible.
Radoman (1973) divided the Balkan hydrobine snails into a number of
families and subfamilies. The Nymphophilinae of North America are equiva-
lent to Radoman's Orientaliidae, with its subfamilies Orientaliinae, Hora-
tiinae, Sadlerianinae, Pseudohoratiinae, Islamiinae, Graecoanatolicinae, Pyr-
gulinae, Chilopyrgulinae, and Ochridopyrgulinae. These subfamilies are
based on the numbers, position, and development of the seminal receptacles
and the bursa copulatrix. The Nymphophilinae is most like the Pseudohora-
tiinae in having a single seminal receptacle 2 and a normal bursa copulatrix.
I feel that greater emphasis is placed on these divisions (families and sub-
families) of the Balkan hydrobiids than is currently justified, especially since
so little is known of the anatomies of the hydrobiids from the rest of the world.
In any event, Nymphophilinae Taylor 1967 is equivalent to and predates Ori-
entaliidae Radoman 1973 and its subordinate groups.
Marstonia is more similar to North American hydrobiid genera than to any
European genus. It is unique among North American groups in having a rela-
tively simple glandular pattern on the verge and a short terminal penis. Other
genera, except Rhapinema, have elaborate patterns of many glands. Rhapi-
nema, like Marstonia, has a single large gland (the apical gland) on the apical
lobe, but it differs by having both a long, slender flagellar penis and a large,
globose shell with a thick rolling parietal callus and columella.
The shell of Marstonia is characterized by its generally narrow shape, gen-







BULLETIN FLORIDA STATE MUSEUM


erally perforate umbilicus, and a small, protruding apical whorl. Among the
eastern North American genera with a lobed verge it overlaps in shell mor-
phology with Cincinnatia and the eastern species placed in Pyrgulopsis.
Species of Cincinnatia are usually more obese, and the eastern species of Pyr-
gulopsis (letsoni, wabashensis, ozarkensis, and scalariformis) are narrower
than most Marstonia.
Marstonia consists of two species lineages. One lineage, found in the Ten-
nessee River system and northward, has a large, squarish apical lobe and a
relatively small, slender penis. The second lineage, found in coastal drainages
of Georgia, has a more elongate apical lobe and a relatively robust penis.

SPECIES OF QUESTIONABLE STATUS

One lot, consisting of two specimens (UMMZ 161894), comes from the
Coosa River, Etowah Co., Alabama. The shell is conical-ovate in shape, has a
narrow umbilicus, and a constricted aperture. These specimens represent an
undescribed species that almost certainly is a Marstonia. It receives no further
discussion because of the scant material available.
Four species currently placed in Pyrgulopsis may actually belong in Mar-
stonia: P. letsoni (Walker), P. wabashensis Hinkley, P. ozarkensis Hinkley, and
P. scalariformis (Wolf). These are small narrow hydrobiids that have in com-
mon a carinate body whorl. The verge of P. letsoni is similar to that of Mar-
stonia, except that it is longer, more slender, and has a small papilliform api-
cal lobe (Berry 1943:43). The anatomy of the type species of Pyrgulopsis, P.
nevadensis (Stearns), is not known. Thus the relationship of Pyrgulopsis to
other genera remains undetermined, and the relationships of the eastern spe-
cies to P. nevadensis need to be corroborated. The generic allocations of the
eastern species placed in Pyrgulopsis require further anatomical studies.

KEY TO THE SPECIES OF Marstonia
1. Verge with an elongate apical lobe; penis large and robust (Fig. 19, A-B). Shell
minute, less than 2.7 mm long at maturity with four or more whorls ... ............... .. 2
la. Verge with a squarish apical lobe; penis short and slender (Fig. 11, A-B). Shell
larger, 3.5 mm long at maturity with 4.5 or more whorls.. ........ ......................... 4
2. Shell thin, fragile, transparent, conical, with an incomplete peristome across the
parietal margin; verge with a single gland on apical lobe. Ocmulgee River Sys-
tem ................................................................................................... agarhecta T hom pson
2a. Shell thick, solid, nearly opaque, ovate-conical; with a complete peristome across
parietal margin; verge with two glands, one on the apical lobe and one near the
base of th e verge ......................................... ............ ... ....... ... .............. ... .. 3
3. Umbilicus wide; shell broadly ovate, 0.70-0.80 times as wide as high; whorls
strongly shouldered, flattened at periphery; suture descending in lateral profile.
O geechee River System ................... ................... ........ ........................... halcyon n. sp.
3a. Umbilicus narrow; shell ovate-conical, 0.66-0.73 times as wide as high; whorls
rounded, not strongly shouldered; suture not descending to the aperture in lateral
profile. Flint River System ...... ... ...................... .... ................. castor n. sp.
4. Shell thick, solid, nearly opaque; umbilicus closed or narrowly rimate...................... 5


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


4a. Shell thinner, transparent or translucent; openly umbilicate ... .......... ... .......... 6
5. Shell ovate-conical in shape, spire convex in outline; outer lip straight in lateral
profile; suture shallow, whorls not shouldered. Verge with two small glands on
apical lobe and a small raised gland near base of verge. Creeks, Limestone Co.,
A lab a m a ... ........... ..... ..... ... ... ..... ........................................................... p a ch y ta n sp .
5a. Shell nearly conical, spire straight sided; outer lip strongly curved in lateral pro-
file; suture deep, whorls shouldered. Verge with a single large gland on the apical
lobe. Tennessee River, Alabama .. ....... arga n. sp.
6. Shell conico-terete in shape; suture deep, producing strongly shouldered whorls;
outer lip slightly arched forward in lateral profile. Owens Spring, Sequatchie,
Marion Co., Tennessee ...................... .. . ogmorhapha n. sp.
6a. Shell ovate-conical or elongate-terete in shape; suture shallow, whorls not
shouldered; outer lip straight in lateral profile ... .. lustrica (Pilsbry), olicacea (Pilsbry)


Marstonia arga new species
DIAGNOSIS.-The verge tapers basally and bears a single apical gland on the apical lobe. The
glandular development of its verge is similar to M. lustrica and M. ogmnorhapha. It further re-
sembles the latter in having a reniform prostate. It differs anatomically from other Marstonia
species in having the bursa copulatrix completely overlapping the posterior pallial oviduct, and
in having the distal half of the bursal duct exposed.
The shell is distinct in being imperforate or at the most narrowly rimate, in having a coni-
cal spire, in having a thick callused ridge inside the aperture, and in having a strongly curved
lip in lateral profile.
SHELL (FIGS. 1A-B; 6A-F).-The shell is medium-sized and conical, with a relatively large
body whorl, and is about 0.52-0.63 times as wide as high. The spire is acutely conical, nearly
straight-sided, and over half the length of the shell. The aperture is about 0.36-0.50 times the
length of the shell. The shell is very thick and opaque or weakly translucent, with a heavy
callused ridge inside the aperture. The umbilicus is weakly rimate or imperforate. The color is
light grayish-brown. The surface is smooth and dull in most specimens. Occasional specimens
have strong, widely spaced vertical -striations and light zones that correspond to growth rest
stages. There are 4.6-5.4 whorls in large specimens (4.7 in holotype). The suture is moderately
impressed. The whorls tend to be flattened along the periphery. The apical whorl is about
0.25 mm in diameter, perpendicular to the initial suture, and projects above the succeeding
whorl. The aperture is irregularly ovate in shape. It is about 0.86-0.96 times as wide as high, and
may be slightly solute in gerontic specimens. The posterior corner is weakly angulate or bluntly
rounded. The peristome extends completely across the parietal wall at maturity. The outer lip
is strongly arched forward in lateral profile, projecting considerably anterior to the posterior
corner and the basal margin. The basal lip is recurved slightly posterior to the columellar margin.
Measurements in mm of 10 paratypes selected to show maximum variation are as follows
(measurements of the holotype are in parentheses): shell length 3.2-3.9 (3.3), shell width 2.1-
2.5 (2.3), aperture length 1.4-1.6 (1.5), aperture width 1.2-1.5 (1.4).
FEMALE (FIG. 7B-C).-The lower female reproductive system is similar to that of M. lus-
trica, except for the following features. The glandular wall of the oviduct loop is comparatively
thin. The seminal receptacle opens directly into the oviduct I and lacks a distinct duct. The
bursa copulatrix projects completely beyond the posterior pallial oviduct. The bursal duct is
exposed for about half its length below the bursa on the mesad surface of the posterior pallial
oviduct.
MALE (FIG. 7A).-The vas deferens I is strongly convoluted above the prostate. The latter
is about twice as long as wide and is roughly kidney-shaped. The vas deferens II is only slightly
convoluted within the coelomic wall and is nearly straight within the verge and penis.
The verge is relatively long and is tapered basally. It bears a single large gland confined to
the tip of the apical lobe. The penis is relatively long and slender.
OPERCULUM (FIG. 25, B).-The operculum is broad and irregularly ovate, thin, transparent,
and slightly amber colored. It is paucispiral, with about 2.5 whorls. The nucleus is in the lower
and right third of the face. The outer surface is weakly striate, with incremental striations.


1977







BULLETIN FLORIDA STATE MUSEUM


DISTRIBUTION (FIG. 8).-Marstonia arga is known only from the Tennessee River in the vicinity
of the Guntersville Reservoir in northeastern Alabama and from Shoal Creek. Although numer-
ous collections of mollusks were made in creeks, rivers, and springs draining into the Tennessee
River between Florence, Alabama, and Chattanooga, Tennessee, this snail was not encountered
except at the above stations.
TYPE LOCALITY.-Guntersville Reservoir, at mouth of Mink Creek, 9.8 mi. SW Scotsboro,
Jackson Co., Alabama. HOLOTYPE: UF 22286, collected 14 September 1973 by Fred G. Thomp-
son. PARATYPES: UF 22287 ( 800), same data as holotype.
SPECIMENS ExAMINED.-TENNESSEE RIVER: ALABAMA. Jackson Co.: Guntersville Reser-
voir, 4.8 mi. SE Scotsboro (UF 22299); 4.3 mi. ESE Scotsboro (UF 22298); 5.1 mi. ESE Scotsboro
(UF 22300); 11.2 mi. SW Scotsboro (UF 22302); mouth of North Sauty Creek, 7.5 mi. SW Scots-
boro (UF 22289); near mouth of Sauty Creek, 8.1 mi. SW Scotsboro (UF 22301); 3.3 mi. SE Holly-
wood (UF 22297). Marshall Co.: Guntersville Reservoir, Honeycomb Creek boat landing, 4.2 mi.
WSW Henryville (UF 22291); south shore of bay S of Honeycomb Creek (UF 22293); small bay
2.1 mi. SW Henryville (UF 22292); Creek Reservation, between Tennessee River miles 356 and
357 (UF 22295); Mill Creek Bay, 5.5 mi. NE Guntersville (UF 22303); Town Creek Bay, 8.8 mi.
NE Guntersville (UF 22288); Street Bluff Bay, 4 mi. WNW Guntersville (UF 22294); Street Bluff
Bay, 3.1 mi. W Guntersville (UF 22290). SHOAL CREEK: ALABAMA. Lauderdale Co.: Shoal
Creek at Lauderdale Co. Hwy. 8 (UF 22306, UF 22308). TENNESSEE. Lawrence Co.: Shoal
Creek, 0.3 mi. NE Iron City (UF 22307).
REMARKS.-This species appears to be favored by the creation of large
quiet bodies of water due to damming of the Tennessee River. It has not yet
been found at lentic stations in the Tennessee River below the Guntersville
Dam, although it undoubtedly occurs there. In Shoal Creek it was collected
in quiet pools of water.
This snail was found most abundantly in beds of Najas in quiet, shallow
water but generally not on other plants. Three genera of aquatic angiosperms
form extensive colonies within the Guntersville Reservoir; Elodea, Myrio-
phyllum, and Najas. Extensive search was made in beds of all three genera,
and only rarely was Marstonia arga found on Myriophyllum. It was never en-
countered on Elodea. Occasional specimens were found on algae-coated
cobbles in water less than two feet deep and in piles of submerged dead tree
leaves.
ETYMOLOGY.-The species name arga is derived from the Greek argos,
meaning white, and refers to the white aperture caused by the thick internal
callus and shell wall.


Marstonia ogmorphaphe new species
DIAGNOSIs.-The verge of this species is most similar morphologically to that of M. lustrica
and of species living in the Tennessee River System because of the enlarged, squarish apical lobe
on the verge and the short, terminal penis. It is more similar to other Marstonia from the Ten-
nessee River System than to M. lustrica in having an elongate reniform prostate. M. ogmorhaphe
is distinguished from all other species of Marstonia by (1) its large size (4-5 mm), (2) its large num-
ber of whorls (5.2-5.8), (3) its deeply incised suture producing strongly shouldered whorls that
are almost flat above, (4) its complete aperture that is broadly ovate in shape with a rounded pos-
terior corner, (5) its outer lip which is slightly arched forward in lateral profile, (6) its thin shell,
(7) its conical-terete shape, and (8) its enlarged bursa copulatrix with a completely exposed duct.
SHELL (FIcs. IC, 9A-E).-The shell is conical-terete in shape. Young specimens are conical-
ovate. Subsequent growth of the last two whorls is progressively lower in position, producing a
terete shape. Large specimens with more than five whorls are about 1.67-1.82 times as long as


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THOMPSON: SNAIL GENUS MARSTONIA


wide. The spire is relatively long, being about 1.56-1.67 times the length of the aperture. The
shell is nearly transparent and thin, light grayish-brown in color, and has a silky luster when free
of encrusting dirt. The umbilicus is narrowly perforate and is partially obscured by the reflected
columellar peristome. There are about 5.2-5.8 whorls in mature specimens (5.4 in holotype). The
first whorl protrudes above the next, and is about 0.25 mm in diameter perpendicular to the
initial suture. The whorls are broadly arched and strongly shouldered with a deeply impressed
suture. The lower whorls are sculptured with well-incised, irregularly-spaced incremental stria-
tions that are usually continuous from the shoulder to the base of the whorl. The aperture is irreg-
ularly ovate in shape, is about 0.82-0.90 times as wide as high, and the upper comer is bluntly
rounded. The peristome extends completely across the parietal wall in shells with four or more
whorls. The aperture lies at an angle of about 12-14 to the axis of the shell, and the outer lip is
slightly arched forward in lateral profile.
Measurements in mm of specimens with 5.2 or more whorls are as follows holotypee measure-
ments in parentheses): shell length 4.0-5.1 (4.4), shell width 2.4-2.8 (2.5), aperture height 1.6-
1.8 (1.7), aperture width 1.4-1.7 (1.4).
OPERCULUM (FIG. 25C).-Ovate, paucispiral, consisting of about two complete whorls. The
nucleus is located in the lower left third of the face. Thin, membranous, amber yellow in color,
transparent. The outer face bears several relatively strong incremental striations.
FEMALE (FIG. 10A-B).-The lower female system contrasts with that of M. lustrica as follows.
The oviduct loop is more convoluted and oppressed flat against the posterior pallial oviduct, as
opposed to being open and transverse to it as in lustrica. The glandular wall is much thinner,
and the seminal receptacle lacks a distinct duct. The bursa copulatrix is very large, being almost
as large as the posterior pallial oviduct, and has the distal 3/4 overlapping the posterior pallial
oviduct. The bursal duct is completely exposed on the mesad surface of the posterior pallial ovi-
duct, almost to its junction with the oviduct II.
MALE (FIG. 11A-C).-The verge is stocky and bears a broad, squarish apical lobe along its
distal left margin. The penis is short and blunt and projects from the end of the verge along the
right side. The apical gland is small and is confined to the inner surface of the tip of the apical
lobe. Other glands are absent.
The vas deferens I is strongly convoluted above the prostate. The latter is about twice as long
as wide and is more or less kidney-shaped. The vas deferens II is only slightly convoluted within
the coelomic wall. It is nearly straight inside the verge and closely parallels the right margin of
the verge and penis.
TYPE LOCALITY.-Owen Springs, Sequatchie, Marion Co., Tennessee. HOLOTYPE: UF
22179; collected 8 September 1973 by Fred G. Thompson. PARATYPES: UF 22180 ( 1000);
same data as holotype.
The spring flows from a large crevice in a limestone ledge. About 100 feet
below its source it forms a narrow, clear, cold creek that broadens intermit-
tently into deeper, quieter. pools. M. ogmorhaphe was found only in quieter
pools within about 100 yards of the spring source, primarily on ooze that was
free of sand and vegetation. Colonies were sporadic and localized.
RANGE (FIG. 8).-This species is known only from the type locality.
ETYMOLOGY.-The specific epithet, ogmorhaphe, is derived from the Greek
ogmos, a furrow, and rhaphe, a seam, and alludes to the deeply impressed su-
ture between the whorls.

Marstonia pachyta new species
DIAGNOSIs.-This species of Marstonia is readily identified by characteristics of both its verge
and shell. Like other Marstonia species, the verge is stocky and has a terminal penis along the
right margin. It shares with M. castor, but not with any other species, a small raised gland on the
ventral surface of the verge. It is unique within the genus in having two small glands along the
left margin of the apical lobe. The shell is readily identified by its ovate-conical shape, its pro-
nounced thickness, and its complete peristome. Other conical-shaped Marstonia have a much


1977








BULLETIN FLORIDA STATE MUSEUM


thinner, almost transparent shell, and the peristome is seldom complete across the parietal margin
of the aperture.
SHELL (Fig. 3A; 12A-E).-The shell is ovate-conical in shape, and is about 1.43-1.70 times
as long as wide. The spire is conical in outline, and exceeds the height of the aperture. The height
of the aperture is about 0.39-0.46 times the length of the shell. The shell is very thick and opaque.
The periostracum is light yellowish-gray in color and has a dull luster. The shell is sculptured
with a few very fine, irregularly-spaced, incremental striations, which become stronger on the
base of the last whorl and occasionally form low wrinkles behind the baso-columellar margin of
the peristome. The umbilicus is imperforate or only narrowly rimate. There are 4.9-5.2 whorls
in mature shells (5.2 in holotype). The whorls have a moderately impressed suture and are moder-
ately arched. There is no tendency for the whorls to be shouldered. The initial whorl protrudes
above the succeeding whorl and is about 0.25 mm in diameter perpendicular to the initial su-
ture. The peristome is complete across the parietal margin of the aperture and may be slightly
solute from the body whorl in some specimens. The outer lip is nearly straight in lateral profile.
The aperture is broadly elliptical in outline, is about 0.80-0.88 times as wide as high, and is
angulate both above and below. The upper corner of the aperture is considerably thickened, as
are the outer and basal walls, whereas the columellar and parietal margins are thinner and nearly
uniform in thickness.
Measurements in mm of mature specimens are as follows holotypee measurements in paren-
theses): shell length 3.3-4.0 (3.9), shell width 2.2-2.5 (2.3), aperture height 1.5-1.7 (1.5), aperture
width 1.2-1.4 (1.3).
OPERCULUM (FIG. 25D).-Relatively elongate, irregularly ovate; thin, transparent, mem-
branous, light amber colored. Paucispiral, consisting of about two rapidly expanding whorls.
The nucleus is located just to the left of midline and is in the lower third of the face. The outer
surface is almost devoid of sculpture and bears only a few incremental striations.
VERGE (FIG. 13A-D).-The verge is moderately stocky and bears a stout penis that projects
from the right distal margin. The region of the apical lobe is not as enlarged as in other Marstonia,
and it usually bears two small apical glands along the left margin and facing toward the snail's
body (Fig. 13, B); however, in one of six specimens examined only a single well developed apical
gland is present, with the second gland being indicated only by a few glandular cells (Fig. 13, D).
In addition, the ventral (inner) surface of the verge bears a small gland raised on a very low pedi-
cel about a fourth of the distance from the base to the apex and to the right of the midline. The
penis and adjacent parts of the verge are dark gray. The remainder of the verge is white.
TYPE LOCALITY.-Limestone Creek, 0.7 mi. E Mooresville, Limestone Co., Alabama. HOLO-
TYPE: UF 22222; collected 1 October 1969 by Fred G. Thompson. PARATYPE: UF 22228 (45);
same data as the holotype.
The creek at the type locality is shallow and consists of alternating
shallow, quiet pools and riffles over broken limestone. Snails were found on
dead leaves and tree rootlets in still shallow water at the edge of a pool.
OTHER SPECIMENS EXAMINED.-Piney Creek, Mooresville, Limestone Co., Alabama (UMMZ
160735).
RANGE (FIG. 8).-This snail is known to occur only in Limestone Creek
and Piney Creek, Limestone County, Alabama.
ETYMOLOGY.-The name pachyta is derived from the Greek pachytes,
meaning thickness, and refers to the characteristically thick shell of this
species.

Marstonia olivacea (PILSBRY)
Amnicola olivacea Pilsbry 1895:115. Walker 1918:135.
DIAGNOSIs.-A thin-shelled Marstonia of dubious systematic status. It is similar to M. lustrica
in its elongate conical shape and its wide umbilicus. It differs by having a relatively inflated
penultimate whorl, a broader operculum, and a darker periostracum.
SHELL (FIGs. 1D, 14A-D).-The shell is elongate-conical, or in some obese specimens ovate-
conical, and is 1.43-1.61 times as long as wide. The periostracum is very thin and grayish-brown.


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


The shell is relatively thin and translucent. The umbilicus is open, moderately wide, and is never
obscured by the peristome. The aperture is 0.41-0.46 times the height of the shell. The spire is
slightly convex in outline. There are 5.0-5.4 whorls (5.4 in holotype), which regularly descend
to the aperture. The apical whorl projects above the succeeding whorl and is 0.25 mm in diam-
eter. The whorls are strongly arched with a moderately impressed suture but are sloped and not
shouldered. The penultimate whorl is slightly rotund. The postembryonic sculpture consists of
fine, close, irregular incremental striations. Occasionally the striations are intensified about the
umbilicus or may be folded into weak thread-riblets, as in the lectotype (Fig. 1, D). The aper-
ture is broadly ovate in outline, is weakly angulate at the posterior corner, and is about 0.83-
0.90 times as wide as high. The plane of the aperture lies at an angle of about 150 to the axis of the
shell. The peristome is usually incomplete across the parietal wall, except in very large individ-
uals. The peristome is very thin, except at the baso-columellar angle, is weakly reflected along
the columella, and is straight in lateral profile.
Measurements in mm of specimens with five or more whorls holotypee measurements in
parentheses) are as follows: shell length 3.9-4.5 (4.35), shell width 2.6-3.0 (2.75), aperture height
1.7-2.0 (1.8), aperture width 1.5-1.7 (1.5).
OPERCULUM (FIG. 25F).-Thin, membranous, light yellow in color, and transparent; pauci-
spiral, broadly ovate in outline, and consists of about 2.5 whorls. The nucleus is located in the
lower quarter and slightly to the left of the midline. The outer surface bears a few fine incre-
mental striations.
VERGE.-Aspects of the soft anatomy are unknown in this species.
TYPE LOCALITY.-[Big Spring Creek], Huntsville, Madison Co., Alabama. LECTOTYPE
by present designation: ANSP 65466a, collected by H. E. Sargent, 1894. PARATYPES: ANSP
65466 (456 specimens); same data as lectotype. The lectotype is a specimen selected by Pilsbry
as the type but apparently never designated as such in print.
RANGE (FIG. 15).-Apparently this species was confined to Big Spring
Creek, which drains south into the Tennessee River. Goodrich (1944:7) stated
that the species was common in streams and springs in and about Huntsville,
but no specimens are available in museum collections other than from Big
Spring Creek. Goodrich (1939:130, 1944:7) also recorded this snail from the
Ogeechee River system in Georgia and the Coosa River system in Alabama,
but his records from both drainages are misidentifications of other species.
This snail probably is extinct. The creek is badly polluted and has been
channelized for most of its course. No specimens were found by the author
during two visits to Big Spring Creek during 1973.
REMARKS.-The specific status of this entity is questionable. Its shell differs
from M. lustrica in having a more inflated penultimate whorl in large speci-
mens, a broader operculum, and a darker periostracum. If M. olivacea was
from a more northern locality, I would be tempted to consider it a synonym
of the highly variable M. lustrica. However, extenuating circumstances dis-
suade me from doing so.
The type locality of M. olivacea is disjunct to the south from the known
geographic range of M. lustrica by nearly 400 miles. This geographic isolation
may not be so great as available data suggest, since almost nothing is known
about the hydrobiid fauna of Kentucky and western Tennessee. On the other
hand, I have collected extensively in the Duck and Buffalo rivers, and in por-
tions of the Cumberland River system in Tennessee without finding Mar-
stonia. It remains to be demonstrated whether or not the genus occurs in lower
courses of the Tennessee River and in western Kentucky and Tennessee.







BULLETIN FLORIDA STATE MUSEUM


Even though the shells of M. olivacea and M. lustrica are very similar,
other distinguishing features, such as the soft anatomy, must be considered.
There are no available preserved anatomical specimens of M. olivacea. I at-
tempted to extract and relax dried bodies from paratypes (ANSP 65466) but
had unsatisfactory results. Because other species (i.e., M. pachyta, M. castor)
differ from M. lustrica in the structure of the verge, it cannot be assumed that
M. olivacea does not.
There is a tendency to conclude that if two forms cannot be distinguished
on the basis of available evidence, they must be identical. In the case of M.
olivacea, I hesitate to draw this conclusion for the reasons mentioned above.
This species' status remains uncertain.

Marstonia lustrica (PILSBRY)
Amnicola lustrica Pilsbry 1890:53.
Amnicola (Marstonia) lustrica Pilsbry; Baker 1926:195; Berry 1943:29-32.
Amnicola winkleyi Pilsbry 1912:1, pl. 1, figs. 9-10.
Amnicola oneida Pilsbry 1917:46: Baker 1928:111-113, pl. 6, figs. 24, 25, 28-31.
Amnicola lustrica gelida Baker 1921:22.
Amnicola gelida Baker 1928:110-111, pl. 6, figs. 19-23.
Amnicola lustrica decepta Baker 1928:108-109, text-fig. 45.
Amnicola lustrica perlustrica Baker 1928:109-110, pl. 6, fig. 15, text-fig. 45.
Marstonia decepta (Baker); Taylor 1960:51, pl. 2, fig. 9; Clarke 1974:244-247, pl. 21, fig. 16.
Marstonia gelida (Baker); Clarke 1974:247, pl. 21, figs. 7-8.
DIAGNOSIS.-The verge is relatively simple in structure and similar to that of M. arga and
M. ogmorhaphe. It has a single apical gland on the apical lobe and a relatively short and stocky
penis. Anatomically the species is unique because of the following features: (1) prostate consoli-
dated and ovate in shape, being only slightly longer than wide; (2) glandular wall of oviduct
loop relatively thick; (3) seminal receptacle borne on a short duct; (4) bursa copulatrix relatively
small, projecting beyond posterior pallial oviduct for about half its length; and (5) bursal duct
completely imbedded in posterior pallial oviduct.
The shell of M. lustrica is distinguished from other Marstonia by the combination of a mod-
erately open umbilicus, conical spire, striate sculpture, and complete peristome that is nearly
straight in lateral profile. The inside of the aperture never bears a thick callus, such as occurs
in M. arga.
SHELL (FIGs. 2A-D; 16A-N).-The shell is dull olivaceous-gray in color, moderately thin, and
weakly translucent or opaque. Occasional specimens may be thick-shelled, but they do not have
heavy calluses deposited inside the aperture. The shell is ovate-conical to elliptical-conical in
shape and generally about 0.55-0.75 times as wide as high. Some extremely narrow specimens
from marshy lakes along the southern edge of the range may be terete. The spire is straightsided
or weakly convex in outline. The aperture is about 0.30-0.45 times the height of the shell. The
base is openly umbilicate. The surface of the shell is sculptured with fine, rather widely-spaced
incremental striatioris that are nearly continuous across the whorls. The suture is deeply im-
pressed. There are about 4.5-6.0 whorls in mature shells. Large terete specimens may have six
or more whorls. The whorls are arched and moderately shouldered. The apical whorl protrudes
and is about 0.25 mm in diameter perpendicular to the initial suture. The remaining whorls in-
crease rather regularly in size. The aperture is broadly elliptical or ovate in shape and is higher
than wide, the posterior corner is weakly angulate or rounded, and the plane of the aperture
lies at an angle of about 150 to the axis of the shell. The peristome generally is complete at ma-
turity. The columellar margin is thin and slightly reflected. The outer lip is nearly straight in
lateral profile.
Measurements in mm for selected specimens representing riverine, lacustrine, and marsh
habitats are shown in Table 1.


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


TABLE 1.-MEASUREMENTS (IN MM) AND WHORL COUNTS FOR SELECTED SPECIMENS OF Marstonia
lustrica, REPRESENTING RIVERINE, LACUSTRINE, AND MARSH HABITATS.


Riverine Lacustrine Marsh

Shell Length 3.3-3.8 3.2-4.3 4.3-4.9
Shell Width 2.2-2.6 2.0-2.4 2.0-2.6
Aperture Height 1.4-1.7 1.3-1.5 1.3-1.6
Aperture Width 1.3-1.5 1.1-1.3 1.1-1.3
Whorls 4.4-4.7 4.9-5.5 5.2-6.0
Shell Width/Length 0.66-0.76 0.53-0.64 0.46-0.56
Aper. H/Length 0.41-0.46 0.35-0.41 0.30-0.36
Aper. H/Aper. W 0.82-0.93 0.80-0.88 0.78-0.93


VARIATION.-Throughout its range M. lacustrica shows a remarkable de-
gree of ecologically-associated variation, as is indicated by the lengthy syn-
onymy for the species. Specimens from lacustrine populations, for which the
name lustrica Pilsbry was proposed (Figs. 2C; 16A-B), are usually more slender
than are specimens from riverine habitats, for which the name decepta Baker
was proposed (Figs. 2A-B; 16G-J). I consider the lake form to be typical of the
species, because it is the most widespread and common variant and is found in
the most commonly occurring habitat throughout its range. Some specimens
from marshy lakes along the southern edge of the snail's range are extremely
elongate or terete (Figs. 2D; 16M-N); these elongate forms were named oneida
Pilsbry and gelida Baker. Two other named forms, winkleyi Pilsbry and per-
lustrica Baker, are minor variations of the riverine form. All degrees of inter-
mediate variation in the shell occur between the various forms, even within
single ecological stations (Turkey Foot Lake, Summit Co., Ohio and Lake
Maxinkuckee, Marshall County, Indiana). I find no other morphological evi-
dence to support recognition of more than one taxonomic entity. However, I
have examined only a limited amount of anatomical material, representing
riverine and lacustrine populations from Ohio and Michigan.
M. lustrica cannot be segregated into distinct subspecies of obvious zoo-
geographic significance. Consequently, I think it unwise to recognize its eco-
logically segregated forms as subspecies until additional evidence is forth-
coming. Two genetic explanations can account for the observed ecologically
associated variation: (1) these forms are different genetic entities that segre-
gate ecologically due to selection for different environmental factors, or (2)
they are genotypic responses to different environmental factors, thus pro-
ducing different phenotypes. If variation is due to the former (1), then our
system of trinomial nomenclature is applicable. If variation results from the
latter (2), then trinomial epithets should not be applied. The terms ecotype
and ecophenotype have been used rather haphazardly in malacology to ex-
plain similar patterns of variation observed among other freshwater mollusks.







BULLETIN FLORIDA STATE MUSEUM


In most cases the use of the term is an indication of ignorance on the part of
the user, for it does not explain the genetic basis of the observed variations.
OPERCULUM (FIG. 25A).-The operculum is simple, ovate, corneous, very light amber-colored,
paucispiral, and consists of about 2.5 whorls. The nucleus is located in the lower right third of the
face. The surface is sculptured with a few fine incremental striations.
FEMALE (FIGs. 5B-C).-The female reproductive system is described for the genus. Specific
characteristics are given above in the diagnosis.
MALE (FIG. 5A).-The verge is relatively stocky. The left margin terminates with a short,
blunt apical lobe that is covered by a relatively large apocrine gland; the right margin ends in a
relatively short, stocky penis. The vas deferens is nearly straight within the verge and penis,
having very little convolution.
TYPE LOCALITIES.-The holotype (ANSP 284061; collected by James Lewis) of Amnicola-
lustrica Pilsbry is from Little Lakes, Wayne Co., New York. The holotype (ANSP 105877; col-
lected by The Rev. Henry W. Winkley) of A. winkleyi Pilsbry is from Saco, York Co., Maine.
The holotype (ANSP 283876; collected by Frank C. Baker, 1916) of A. oneida Pilsbry is from
Lower South Bay, Oneida Lake, Madison Co., New York. The holotype (University of Illinois
Natural History Museum, P 926) of A. gelida Baker is from a post-Wisconsin deposit at Morris,
Grundy Co., Illinois. The holotype (University of Illinois Museum of Natural History Z22501) of
A. decepta Baker is from Silver Lake, Waukesha Co., Wisconsin. The holotype (University of
Illinois Museum of Natural History Z18365a) of A. perlustrica Baker is from the shore of Lake
Michigan, E of Sturgeon Bay, Door Co., Wisconsin.
I have examined the holotypes of lustrica, winkleyi, and oneida; but not those of gelida, de-
cepta, or perlustrica.
RANGE (FIG. 15).-Marstonia lustrica is widely distributed from Maine and
New York west through northwestern Pennsylvania, Ohio, northern Indiana,
and northern Illinois to Iowa and Minnesota. The northern limits of its known
range are in southern Quebec and Ontario. Clark (1973:245) recorded it from
the Moose, Albany, and Winnipeg river systems in Ontario. These records are
included on my distribution map, though I have not examined the specimens.
Two southern records, one each from Missouri and Virginia, need to be con-
firmed with new material.
SPECIMENS EXAMINED.-ILLINOIS. COOK Co.: Chicago, Lake Michigan (MCZ 2221); Berry
Lake, nr. Chicago (CM 62.24230); DEKALB Co.: DeKalb (MCZ 46577); FULTON Co.: Canton
(FMNH 19976, UMMZ 69847); LAKE Co.: Highland Park, beach at Lake Michigan (USNM
523790); MASON Co.: (FMNH 9851); Illinois River above Havana (FMNH 15687); MCHENRY
Co.: Algonquin, Fox River (FMNH 71860); ROCK ISLAND Co.: Rock Island (USNM 476863); WILL
Co.: Joliet (FMNH 58692); Joliet, DuPage Crossing (FMNH 65031); Joliet, Lillycache Creek
(CM). INDIANA. KOSCIUSKO Co.: Turkey Lake (UMMZ 120595, FMNH 87888); LAKE Co.:
Berry (FMNH 112724); Lake Michigan, Millers (CM); Millers, Calumet River (UMMZ 120605);
LA PORTE Co.: Pine Lake (UMMZ 69846, UMMZ 120618, MCZ 167502); MARSHALL CO.:
Maxinkuckee Lake (CM, UMMZ 69045, FMNH 87850, USNM 541981, MCZ 71291); PORTER
Co.: Tremont Dunes Park, beach drift (FMNH 157441); Indiana Dunes State Park (FMNH
114682); STEUBEN Co.: Pleasant Lake (USNM 346866, UMMZ 27572); Turkey Lake (CM). IOWA.
DICKINSON Co.: Canal, Upper Gar Lake (USNM 508447); Lake Okoboii (USNM, 30 lots); Or-
leans (USNM 478427); Spirit Lake (USNM 514552, FMNH 130405); Arnold's Park (UF 22218-
22221); MUSCATINE Co.: (USNM 510611); ScoTTr Co.: Davenport, Mississippi River (USNM
528018). MAINE. YORK Co.: Saco (ANSP 105877). MICHIGAN. ALLEGAN Co.: Green Lake
(UMMZ 120657, USNM 508421); BARRY Co.: Long Lake, 1 mi. NE Cloverdale (UMMZ 197694,
USNM 622765); BERRIEN Co.: Niles (CM); BENZIE Co.: Crystal Lake (UMMZ 120656); BRANCH
Co.: St. Joseph River, Union City (UMMZ 197695, USNM 622754); Marble Lake, nr. Quincy
(UMMZ 164280); CALHOUN Co.: Ackley Lake, 9 mi. N Marshall (UMMZ 197709); 7.5 mi. S Battle
Creek, Graham Lake (USNM 622764); Battle Creek River, 4.5 mi. NE Battle Creek (UMMZ
197692); Outlet of Hall's Lake, 2.5 mi. E Battle Creek (UMMZ 197711); Battle Creek, Bailey
Park, Battle Creek River (UMMZ 171790); CHARLEVOIX Co.: Deer Lake (UMMZ 29586); Barney


Vol. 21, No. 3






THOMPSON: SNAIL GENUS MARSTONIA


Lake, Beaver Island (UMMZ 142517); Lake Michigan, Beaver Island, High Island Harbor (MCZ
30719, CM, FMNH 87849); CHEBOYGAN Co.: Outlet, Carp Lake (CM); Emmet, Carp Lake
(UMMZ 120659); Carp Lake, nr. Mackinaw City (CM); DICKINSON Co.: Brown Lake (UMMZ
7421); EATON Co.: Battle Creek River, W Bellevue (CM 62.2757); CRAWFORD Co.: Manistee
River, 7 mi. N Lake Mararethe (UMMZ 132277); GENESEE Co.: Silver Lake, nr. Fenton (UMMZ
41928); GRAND TRAVERSE Co.: Traverse City, Pine Lake (UMMZ 120711); HURON Co.: Rush
Lake (UMMZ 7417); IONIA Co.: Long Lake (UMMZ 164293); IRON Co.: Pickerel Lake (UMMZ
150145); JACKSON CO.: Sandstone Creek, 5 mi. W Jackson (UMMZ 197701, USNM 622766); Con-
cord, Michigan Spring Branch (UMMZ 197690); KALAMAZOO Co.: Outlet of Gourdreck Lake,
3 mi. NW Vicksburg (UMMZ 197691); W side Gull Lake (UMMZ 197706); 1.5 mi. N-NW Climax,
Blue Lake (USNM 622759); KEEWENAW Co.: Davis Creek (UMMZ 160672); Isle Royale, W end
Rock Harbor (UMMZ 120706); KENT Co.: Perch Lake (CM); Grand Rapids (UMMZ 120650);
Dewey's Mill (FMNH 87890, USNM 697029); Byer's Trout Pond (CM); Grand Rapids, Reed's
Lake (FMNH 102341, USNM 254122a); Perch Lake (CM, UMMZ 120651); LAKE Co.: Marl Lake
(UMMZ 160649); Kinney Creek (CM, FMNH 87893); Pere Marquette River (FMNH 87889);
Lake Twp., Bass Lake (UMMZ 37619); LENAWEE Co.: Posey Lake Outlet (UMMZ 46659);
LIVINGSTON Co.: Whitewood Lake (UMMZ 120703, UMMZ 27571); MANISTEE Co.: Onekama
(FMNH 59991); Bear Lake (USNM 172303); MONROE Co.: La Paisance Bay (UMMZ 27548);
MONTCALM Co.: outlet Mud Lake, Riverdale (UMMZ 120677); Cedar (UMMZ 120667); Mus-
KEGON Co.: Blue Lake (MCZ 166005); Muskegon Lake (UMMZ 120678); NEWAYGo Co.: Mono
Lake (USNM 539420); Hess Lake (MCZ 166003, FMNH 122002); Brook's Lake (FMNH 105144,
UMMZ 120675); Hog Lake (MCZ); Pickerel Lake (UMMZ 120668); OAKLAND Co.: Deer Lake
nr. Clarkston (UMMZ 7568); Orchard Lake (CM, UMMZ 69849); Straits Lake (UMMZ 29591);
Huron River, above Milford (UMMZ 29591); PRESQUE ISLE Co.: Orchard Lake (CM); Black Lake
(FMNH 87853); OGEMAN Co.: Edwards Lake (UMMZ 41927); WASHTENAW Co.: Delhi Mills,
Huron River (USNM 622758, UMMZ 197702); Black Lake (FMNH 59990); Ann Arbor (FMNH
122786); Halfmoon Lake (UMMZ 46646); Ann Arbor, Huron River (FMNH 87891); nr. Ann Arbor
(USNM 444141). Kankakee River, English Lake (CM 42). MINNESOTA. BLUE EARTH Co.: Eagle
Lake (USNM 123902); DOUGLAS Co.: Alexandria, Lake Mary (USNM 347707); HENNEPIN Co.:
Mississippi River (CM 62.16279); nr. Minneapolis, Lake Harriet (FMNH 58691) nr. Minneapolis,
Kegans Lake (MCZ 2225); nr. Minneapolis, Lake Harriet (UMMZ 120609); ITASCA Co.: (FMNH
59987); PINE Co.: St. Croix River e. of Rock Creek (USNM 514469, 514470); STEARNS Co.: Kim-
berly, Rice Lake (USNM 347727); Birch Lake (UMMZ 120622); WRIGHT Co.: Clearwater Lake
(UMMZ 143680). MISSOURI: SHANNON Co.: Jacks Fork (MCZ 2224). NEW YORK. Hudson
River drift (CM); Mohawk River (USNM 24777, USNM 97910); ALBANY Co. Albany, Normans
Hill (MCZ); ERIE Co.: Grand Island (FMNH 114728); HERKIMER Co.: Little Lakes (USNM 28085,
FMNH 102421, FMNH 32841); Mohawk (UMMZ 120590, MCZ 53879); Erie Canal (USNM
121320); MADISON Co.: Lower South Bay, Oneida Lake (type lot Amnicola oneida Pilsbry);
ORLEANS CO.: Cedar Lake, nr. Albion (USNM 572662, USNM 572665); OTSEGO Co.: Outlet
Schuyler's Lake (USNM 27895); Schuyler's Lake (UMMZ 27554, MCZ 2107, USNM 514615);
WAYNE CO.: nr. Blyde (USNM 251446); YATES Co.: Seneca Lake (MCZ 2108); RYE Co.: Little
Lake (FMNH 121117); WAYNE Co.: Sodus Bay (USNM 536640); Little Lakes (ANSP 74564, ANSP
122196); Skaneateles Lake (ANSP 95480); OSWEGO Co.: Barge Canal, 0.5 mi. SE Hinonansville
(ANSP 113115). NEW BRUNSWICK. Portland, Harrigan's Lake (FMNH 107179). OHIO. ASH-
LAND CO.: Outlet of Long Lake (CM 62.24923); CHAMPAIGNE Co.: Cedar Swamp, nr. Urbana
(US 22223); CLARK CO.: Midway (UF 22227); ERIE Co.: Sandusky (CM); Cedar Point (CM
62.24730); LUCAS Co.: Maumee River, Hocking Valley Docks (UMMZ 27549); OTTAWA Co.:
Sandusky Bay Point (UMMZ 27556); PORTAGE Co.: Cuyahoga River, nr. Hiram (CM 31); Gar-
retsville (CM); STARK Co.: Tuscarawas River, Navarre (CM); SUMMIT Co.: Mud Lake (CM
62.24922); Hudson (UMMZ 69850); Hudson, Tinkers Creek (MCZ 15129, CM 62.25396, FMNH
71861); Big Reservoir (CM 62.24924); Long Lake (CM 62.25209); Springfield Lake (CM); Tus-
CARAWAS CO.: Side-cut on Mill-Race, New Philadelphia (CM); ditch from small swamp on river,
s.e. New Philadelphia (CM); Tuscarawas River, New Philadelphia (CM); swamp below Blakes
Mills, nr. New Philadelphia (CM); mill race, Tuscarawas River, New Philadelphia (CM); small
swamp s.e New Philadelphia (CM); New Philadelphia (USNM 117749). ONTARIO. ADDING-
TON & LENNOX Cos.: Ernestown, Wilton Creek (MCZ 244172); Camden, Varty Lake (MCZ
244183) Adolphustown Twp. Hay Bay (MCZ 234626); Camden, Camden Lake (MCZ 248086);






BULLETIN FLORIDA STATE MUSEUM


Richmond, Salmon River (MCZ 248075); Bay of Quinte, Adolphustown (ANSP 234653); BiUCE
Co.: Pond nr. South Hampton (FMNH 130428); CANTWELL Co.: stream, Mono Mills (UMMZ
133232); HASTINGS Co.: Hungerford, Dry Lake (MCZ 248101); Huntingdon, Moira Lake (MCZ
248115); HAMILTON Co.: (ANSP 67569); Lake Simcoe (UMMZ 120625); Lake Huron, Cohome,
Georgian Bay (ANSP 105668) Giants Tomb. Id., Georgian Bay (ANSP 105667); Cohome,
Georgian Bay (ANSP 105744); Lake Huron, Gravelly Point, St. Joseph's Id., North Channel
(ANSP 153108); LAMBTON Co.: Lake Huron, Kettle Point (UMMZ 133273); Manitou Island,
s.e. side of Lake Mendemoa (UMMZ 52633); PRINCE EDWARD Co.: Lake Ontario (UMMZ
138771); Athol Twp., Lake Ontario, Athol Bay (MCZ 248034); Matheson, Black River (MCZ
248047). Rochester, Lake Ontario (CNHM 121181); TRONTENAC Co.: Kingston (MCZ 244222);
Wellington, w. Lake, Ontario, Shore 300 yds. w. of Harbour Pier, Wellington (USNM 464527).
PENNSYLVANIA. ERIE Co.: Presque Isle, Long Pond (CM 62.24729); Presque Isle, Middle
Bend (CM 62.24731); Presque Isle, sand flats (CM 62.24728). VIRGINIA. Nr. Alexandria (CM).
WISCONSIN. DANE Co.: Madison (FMNH 115418); Lake Mendota (CM 62.26283); DooR Co.:
Newport, Newport Beach (FMNH 157444); MARINETTE Co.: North Woque Bay (UMMZ 120612);
MILWAUKEE Co.: Milwaukee (USNM 7 lots); VILAS Co.: Rest Lake (FMNH 25727).
REMARKs.-This snail has a wide geographic distribution within the cool
temperate areas of North America's Great Lakes region. Within its range it
occupies a wide variety of habitats, including lakes, ponds, marshes, rivers,
and small streams. Most specimens that I examined came from habitats that
were characterized by clear water with submerged aquatic plants. Though it
is widely distributed, it is not known from geologic deposits older than the
Wisconsin Glacial Period, nor from fossil localities outside its present range
(Taylor 1960).
Marstonia lustrica appears to be a species that originated in the upper
Mississippi River system during the Wisconsin Glacial Period as a cold-
tolerant member of Marstonia. It apparently moved north with the receding
glacier, where it came to be widely distributed throughout the Great Lakes
region.

Marstonia halcyon new species
DIA(;NOsis.-This species is distinguished by a small, broadly ovate shell with a deep suture
producing strongly shouldered whorls, a flattened periphery on the whorls, a wide umbilicus,
and complete peristome that is nearly uniformly thick. The suture descends to the aperture in
lateral profile. M. halcyon is related to M. castor and M. agarhecta, based on its slender apical
lobe on the verge with a small apical gland on the mesad surface of the tip and an enlarged penis.
It also shares with M. castor a small raised tubercular gland on the mesad surface of the verge,
but differs in this regard from M. agarhecta, which has only the apical gland.
In addition to the characteristics of the verge, this snail differs from AM. lustrica and its allies
in having a slender copulatory bursa that does not extend to the end of the posterior pallial ovi-
duct and is nearly completely imbedded in glandular tissue.
SHELL (FIGS. 3D, 17A-E). -The shell is small, usually less than 2.5 mm long, and is broadly
ovate in shape, being about 0.70-0.80 times as wide as high. The spire is as long as, or longer than
the aperture and is slightly convex in outline. The aperture is about 0.40-0.50 times the length
of the shell. The shell wall is nearly of uniformly moderate thickness and is almost transparent.
Specimens with a complete peristome usually develop a slight callused ridge within the peri-
stome. The periostracum is a very delicate light gray in color. The umbilicus is rather broadly
perforate. The whorls are densely sculptured, with fine irregular incremental striations that are
crossed by much finer spiral striations. There are about 4.0-4.3 whorls at maturity (4.3 in holo-
type); large gerontic specimens may have as many as 5.0 whorls. The suture is deeply impressed,
causing the whorls to be almost flat-topped and shouldered. The periphery of the whorls are dis-
tinctly flattened, with the apical whorl protruding above the succeeding whorls. The body whorl


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


becomes ventrad in position and is usually constricted at the aperture, where it descends rather
noticeably (Fig. 17B, lateral profile). The aperture is oval in outline, broadly rounded at the pos-
terior comer when mature, and about 0.80-0.93 times as wide as high. The aperture is adnate to
the preceding whorl for a short distance along the parietal margin. The peristome is nearly
straight in lateral profile and lies at about 350 to the shell axis.
Measurements in mm for specimens with a complete peristome are as follows holotypee
measurements in parentheses): shell length 2.0-2.5 (2.3), shell width 1.6-1.9 (1.75), aperture
height 1.0-1.1 (1.0), aperture width (0.8-1.0 (0.9).
Occasional gerontic specimens reach a length of 3.3 mm and are proportionately more
slender than smaller specimens because of the ventrad position of the body whorl. Occasional
small males of about 1.8 mm long may develop a complete peristome.
OPERCULUM (FIG. 25G).-The operculum is paucispiral, ovate, thin, transparent, membranous,
and light yellowish-white in color. It consists of about two whorls and is sculptured on the outer
surface with fine irregular incremental striations.
FEMALE (FIGs. 18A-B).-The female reproductive system is similar to that of 11. lustrica and
related forms, except as follows: (1) the oviduct loop is vertical to the axis of the pallial oviduct;
and (2) the bursa copulatrix does not overlap the posterior end of the pallial oviduct and is com-
pletely imbedded in the posterior pallial oviduct, except for its distal tip.
MALE (FIGS. 19A-C).-The vas deferens I is only moderately convoluted and is only slightly
thickened in the region of the convolutions. The prostate is relatively elongate and rather dis-
tinctly lobed, in contrast to the more concentrated prostate in XM. lustrica. The verge originates
on the nape on the right of the middorsal line and is forked distally. The penis is considerably
longer and more enlarged than the apical lobe. The latter is papilliform and bears a single, small
apical gland on the ventral side of its tip. A second small, raised gland is present on the ventral
surface of the verge about halfway between the base and the apical lobe.
DISTRIBUTION (FIG. 20).--M. halcyon is confined to the lower half of the Ogeechee River
System in eastern Georgia, where it is found in quiet water over a silt or sand bottom. It has been
collected only in the Ogeechee River and Buckhead Creek, though it probably occurs in other
creeks along the middle and lower course of the Ogeechee River.
TYPE LOCALITY.-Buckhead Creek, 0.6 mi. W Miller, Jenkins Co., Georgia. HOLOTYPE:
UF 22312; collected 6 October 1974 by Fred G. Thompson and Beverly E. Johnson. PARA-
TYPES: UF 22313; same data as the holotype.
At the type locality, Buckhead Creek is about 3-5 ft deep, with a hard sand bottom and a
slight current. Snails were collected in quiet, shallow water on silty sand and in clusters of fila-
mentous algae.
SPECIMENS EXAMINED.-GEORGIA. BRYAN Co.: Ogeechee River, 1.1 mi. SE Blichton (UF
22318); EFFINGHAM CO.: 1.7 mi. SW Guyton (UF 22316, 22319); JENKINS Co.: Buckhead Creek,
0.6 mi. W Miller (UF 22311); SCREVEN Co.: Ogeechee River, 0.7 mi. SW Ogeechee (UF 22310,
22314); Ogeechee River, 1.6 mi. SW Halcyon Dale; Ogeechee River, 3.0 mi. SW Oliver (UF
22320).
REMARKs.-This snail was always collected in open water, primarily on
silty sand. Only rarely was it found on filamentous algae. On no occasion was
it found on dead submerged leaves, moss, or other detritus, although other
hydrobiids (Amnicola sp. and Lyogyrus sp.) were abundant on such substrates.
Goodrich (1939:130) recorded four species of hydrobiids from the Ogee-
chee River. His material was not available to me for examination, as it is being
studied by another investigator. I cannot state the name(s) under which Good-
rich recorded M. halcyon.
ETYMOLOGY.-In the area where M. halcyon was found, the Ogeechee
River is gentle and quiet, bordered with large cypress trees and hardwood
forests. The species name is borrowed from the Greek halcyon, a mythological
sea bird that brought peace and serenity wherever it alighted. The name is
suggested by one of the places near where it was collected, Halcyon Dale.


1977







BULLETIN FLORIDA STATE MUSEUM


Marstonia castor new species
DIAGNOSIS.-Marstonia castor is a minute snail, less than 2.5 mm long, ovate-conical in shape,
relatively thick and solid, and has about 3.9-4.4 rounded whorls with a deeply impressed suture.
The peristome is complete at maturity, and the umbilicus is narrowly perforate. The verge has a
tubercular gland on the mesad surface in addition to the apical gland.
SHELL (FIGs. 3C, 21A-D).-The shell is minute, ovate-conical in shape, and about 0.66-0.73
times as wide as high. It is narrowly but distinctly umbilicate. The circum-umbilical area is almost
obtusely angulate. The shell is moderately thick for its size, semi-transparent, and light gray in
color. The spire is slightly convex in outline and slightly longer than the aperture, which is about
0.44-0.49 times the length of the shell. There are 3.9-4.4 Whorls in mature shells. Females tend
to be slightly larger than males and have about 0.3 more whorls. The apical whorl is raised and
rounded with a well-impressed suture, and is about 0.23-0.24 mm in diameter perpendicular
to the initial suture. Post-apical whorls have a deeply impressed suture, are strongly and evenly
arched, and have numerous fine incremental striations. The aperture is ovate in shape and about
0.81-0.91 times as wide as high. In lateral profile the plane of the aperture lies at about 18-20
to the axis of the shell. The peristome is complete across the parietal margin at maturity and is
neither advanced nor receded in lateral profile. The outer lip is sharp, nearly rounded to the
columella, and may develop a relatively thick internal callus. The parietal margin of the aper-
ture is nearly straight.
Measurements in mm of six adult specimens selected to show the range of variation are as
follows holotypee measurements in parentheses): shell length 1.94-2.70 (2.30), shell width 1.40-
1.98 (1.51), aperture height 0.94-1.33 (1.05), aperture width 0.83-1.08 (0.86).
OPERCULUM (FIG. 25E).-Broadly ovate in shape, paucispiral, and consisting of about two
whorls, with the nucleus located in the lower left quarter. Thin, membranous, transparent. The
outer surface shows a few fine incremental striations.
VERGE (FIG. 22A-B).-The verge is relatively slender and has a relatively enlarged penis,
which is about twice the length of the apical crest. The apical crest is nearly completely covered
by an apical gland. On the ventral side near the middle of the verge is a small globular gland
raised on a low pedicel.
TYPE LOCALITY.-Cedar Creek, 3.4 mi. S-SW Coney, Crisp Co., Georgia. HOLOTYPE: UF
22176; collected 19 November 1973 by Fred G. Thompson. PARATYPES: UF 22177 (51); same
data as the holotype.
In addition to the type series, I have examined about 300 other specimens
from the type locality (UF 22178).
The type locality is a small clear stream that flows through a cypress
slough and drains into the east side of Lake Blackshear, a reservoir on the Flint
River. Snails were generally distributed in the creek on Najas and to a lesser
extent on clumps of Chara in shallow clear water that had only a slight cur-
rent. They were not found on the substrate or debris. At no place was the snail
abundant.
RANGE (FIG. 20).-This snail is known only from the type locality.
ETYMOLOGY.-The species epithet castor is taken from the generic name of
the beaver, Castor canadense, with which it shares the type locality.

Marstonia agarhecta THOMPSON
MAarstonia agarhecta Thompson 1969:243-247; fig. IA-F.
DIAGNOSIS.-This is a minute snail most closely related to Al. castor by the structure of the
verge, which bears a single enlarged epidermal gland on the apical lobe but lacks other glands.
The penis is relatively large and about twice the length of the apical lobe. The shell is minute
(about 2.3-2.7 mm long), conical, and very fragile. It has an incomplete peristome and about 4.4-
4.6 whorls that are separated by a deeply impressed suture.
SHELL (FIGs. 3B, 23A-D).-The shell is minute, very thin and fragile, transparent, conical,


Vol. 21, No. 3








THOMPSON: SNAIL GENUS MARSTONIA


and about 0.64-0.74 times as wide as high. It is dimorphic in shape. Females tend to be broader
than males. The spire is about equal to the aperture in height and nearly straightsided. The um-
bilicus is open but narrowly perforate. There are 4.4-4.6 whorls in adult shells. The apical whorl
is 0.23-0.25 mm in diameter perpendicular to the initial suture; protrudes above the succeeding
whorl; is strongly rounded with a deep suture; and has very fine, close microscopic striations.
The following whorls are strongly rounded with a deeply impressed suture. The body whorl is
weakly shouldered. The sculpture on the lower whorls consists of very fine, close incremental
striations that are equal in intensity over the surface of the whorls. The aperture is ovate, about
0.77-0.83 times as wide as high, and about 0.45-0.52 times the height of the shell. The greatest
diameter of the aperture lies at about 300 to the shell axis. The plane of the aperture is slightly
oblique to the shell axis in lateral profile. The peristome is incomplete across the parietal wall.
The parietal callus consists only of a very thin glaze. The columellar lip is concave, very thin,
and weakly reflected. The outer lip is weakly arched forward above the periphery and slightly
recessed near the base.
Measurements are given in mm for large specimens as follows holotypee measurements in
parentheses): shell length 2.3-2.7 (2.65), shell width 1.6-1.95 (1.75), aperture height 1.1-1.3 (1.2),
aperture width 0.9-1.05 (0.95).
OPERCULUM (FIG. 25H).-Broadly ovate in shape, with a slight indentation along the parietal
margin. It is very thin, membranous, and colorless or only slightly tinged with yellow. It is pauci-
spiral with about 2.5 whorls. The nucleus is large and located in the lower left third of the face.
The outer surface is sculptured with a few fine incremental striations.
VERGE (FIG. 24A-B).-The verge is stout and slightly compressed dorso-ventrally. The distal
left margin terminates in an apical lobe that bears an enlarged apical gland. The penis is rela-
tively slender, long, and enlarged.
RADULA.-Minute, about 450 u long and contains about 42-46 transverse rows of teeth (10
specimens examined). The central tooth is about 19 /L wide and bears an enlarged mesocone
with 3-5 ectocones and a single basocone on each side. The lateral tooth bears 2-1-4 to 3-1-5 cusps.
TYPE LOCALITY.-Bluff Creek, 10.4 mi. S-SE Hawkinsville, Pulaski Co., Georgia. HOLO-
TYPE: UF 20528; collected 31 January 1969 by Fred G. Thompson. PARATYPES: UF 20529
(296); same data as the holotype.
Specimens were found in clear water with only a slight current, predomi-
nantly in diatomaceous ooze on top of old submerged logs. Occasionally indi-
viduals were also found in silt that contained large amounts of diatoms.
RANGE (FIG. 20).-This species is known only from the type locality.
REMARKs.-Though very different in shell structure, this snail is most
closely related to M. castor. Both species are alike in having an enlarged, elon-
gate penis and a relatively enlarged and protruding apical lobe. In these re-
spects the two species differ remarkably from other Marstonia.


LITERATURE CITED

Baker, F. C. 1926. Nomenclatorial Notes on American Fresh Water Mollusks. Trans. Wisconsin
Acad. Sci., Arts, Let. 22:193-205.
1928. The Freshwater Mollusca of Wisconsin, Pt. 1. Gastropoda. Bull. Wisconsin
Geol. Nat. Hist. Surv. 70:i-xx, 1-507, pls. 1-28.
Berry, E. G. 1943. The Amnicolidae of Michigan: Distribution, Ecology, and Taxonomy. Misc.
Publ. Mus. Zool., Univ. Michigan 57:1-68.
Boeters, H. D. 1970. Die Gattung Microna Clessin, 1890 (Prosobranchia, Hydrobiidae). Archiv
fur Molluskenkunde 100:113-145.
1971. Pseudamnicola Paulucci, 1878 und Mercuria n. gen. (Prosobranchia, Hydro-
biidae). Archiv fur Molluskenkunde 101:175-181.
1974. Westeuropaische Hydrobiidae, 5. Horatia Bourguignet, Plagigeyeria Tomlin
und Litthabitella Boeters (Prosobranchia). Archiv fur Molluskenkunde 104:85-92.







BULLETIN FLORIDA STATE MUSEUM


Clarke, A. H. 1973. The Freshwater Molluscs of the Canadian Interior Basin. Malacologia
13:1-509.
Gregg, W. 0. and D. W. Taylor. 1965. Fonticella (Prosobranchia: Hydrobiidae), A new genus of
West American Freshwater Snails. Malacologia 3:103-110.
Goodrich, C. 1939. Certain Mollusks of the Ogeechee River, Georgia. Nautilus 54:129-131.
1944. Certain Operculates at the Coosa River. Nautilus 58:1-15.
Morrison, J. P. E. 1949. The Cave Snails of Eastern North America. Ann. Rept. Amer. Malac.
Union 1948:13-15.
Pilsbry, H. A. 1890. Preliminary Notices of New Amnicolidae. Nautilus 4:52-53.
1895. New American Freshwater Mollusks. Nautilus 8:114-116.
1912. A New Species of Amnicola. Nautilus 24:1, pl. 1, figs. 8-9.
1917. Amnicolidae from Oneida Lake, N. Y. Nautilus 31:44-46.
Radoman, P. 1966. Die Gattungen Pseudamnicola und Horatia. Archiv fur Molluskenkunde
95:243-253.
1967. Revision der Systematik einiger Hydrobiiden Arten aus dem Obiid. Archiv
fur Molluskenkunde 96:149-154.
1972. Nochmals uiber die Gattung Pseudamnicola und Schliesslich die Gattung
Orientalia n. gen. Archiv fur Molluskenkunde 102:195-200.
1973. New Classification of Fresh and Brackish Water Prosobranchia from the
Balkans and Asia Minor. Mus. d'Hist. Nat. Beograd. (Posebna Izdanja) 32:1-30.
Taylor, D. W. 1960. Late Cenozoic Molluscan Faunas from the High Plains. U.S. Geol. Surv.
Prof. Pap. 337:1-94, pls. 1-4.
8-19- 1966. A Remarkable Snail Fauna from Coahuila, Mexico. Veliger 9:152-228, pls.
8-19.
Thompson, F. G. 1968. The Aquatic Snails of the Family Hydrobiidae of Peninsular Florida.
Univ. Florida Press, Gainesville. 268 pp.
--__ 1969. Some Hydrobiid- Snails from Georgia and Florida. Quart. J. Florida Acad.
Sci. 32:242-265.
Walker, B. 1918. A Synopsis of the Classification of the Freshwater Mollusca of North America,
North of Mexico, and a Catalog of the More Recently Described Species, with Notes. Misc.
Publ. Mus. Zool., Univ. Michigan (6): 1-213.


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


1mm
FIGURE 1.-(A, B) Marstonia arga new species, HOLOTYPE: UF 22286; (C) Marstonia ognior-
haphe new species, HOLOTYPE: UF 22179; (D) Marstonia olivacea (Pilsbry), LECTOTYPE:
ANSP 65460a.


1977







BULLETIN FLORIDA STATE MUSEUM


C D
lmm
FIGURE 2.-Marstonia lustrica (Pilsbry): (A, B) Riverine form; Cedar Swamp, nr. Urbana, Cham-
paigne Co., Ohio (UF 22223); (C) Lacustrine form; Hess Lake, Newaygo Co., Michigan (UF
22190); (D) Extremely slender lacustrine form; Turkeyfoot Lake, Summit Co., Ohio (UF 22225).


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA






I 'V


1mm


1mm








4-A*


1mm 1mm

FIGURE 3.-(A) Marstonia pachyta new species, HOLOTYPE: UF 22222; (B) Marstonia agar-
hecta Thompson, HOLOTYPE: UF 20528; (C) Marstonia castor new species, HOLOTYPE: UF
22176; (D) Marstonia halcyon new species, HOLOTYPE: UF 22312.






BULLETIN FLORIDA STATE MUSEUM


FIGURE 4.-Scanning Electron Micrographs of North American hydrobiid snail embryonic sculp-
ture: (A) Rhapinema dacryon Thompson (UF 22378) X196; (B) Cincinnatia integra (Say) (UF
22189) X224; (C) Notogillia wetherbyi (Dall) (UF 22191) X245; (D) Marstonia hlstrica (Pilsbry)
(UF 22190) X203; (E) Marstonia ogmorhaphe new species (UF 22180) X214; (F) Marstonia arga
new species (UF 22287) X210; (G) Marstonia agarhecta Thompson (UF 20529) X224; (H) Mar-
stonia castor new species (UF 22177) X196; (I) Marstonia halcyon new species (UF 22313) X166.


Vol. 21, No. 3


r, LZ_ , N






apical gland


vas deferens II apical
lobe

A /-. -penis
prostate \

verge




vas deferens I
coelomic
wall


/posterior pallial oviduct

anterior f
pallial j .'/ / ""
oviduct 7,, / bursa copulatrix

B /K seminal receptacle
i\ / gpd
vagina
oviduct Iovary




,~ ^ -albumen gland


oviduct II- ~ sr bursa copulatrix

1mm oviduct I
FIGURE 5.-Marstonia lustrica (Pilsbry); Midland, Clarke Co., Ohio (UF 22227). (A) male repro-
ductive system; (B) female reproductive system; (C) oviduct and associated structures freed from
the pallial oviduct; gpd = gonopericardial duct, sr = seminal receptacle.







BULLETIN FLORIDA STATE MUSEUM


A B


1mm rF

FIGURE 6.-Marstonia arga new species: (A, B) HOLOTYPE (UF 22286); (C-F) PARATYPES
(UF 22287).


.Vol. 21, No. 3






body wall
apical gland
A

prostate

posterior wall of
mantle cavity o\




vas deferens /I7
penis

vas deferens I




B /- posterior pallial oviduct



anterior pallial


oviduct II seminal receptacle
coviduct I










oviduct bursa copulatrix
gpd
seminal receptacle
1mm oviduct I

FIGURE 7.-Marstonia arga new species: (A) male reproductive system; (B) female reproductive
system intact except for the ovary; (C) oviduct and associated structures freed from the pallial
oviduct; gpd = gonopericardial duct.






BULLETIN FLORIDA STATE MUSEUM


A pachyta arga ogmorhaphe

FIGURE 8.-The geographic distribution of Marstonia in the Tennessee River System.


Vol. 21, No. 3






THOMPSON: SNAIL GENUS MARSTONIA


A B


D E


1mm

FIGURE 9.-Marstonia ogmorhaphe new species: (A, B) HOLOTYPE (UF 22179); (C-E) PARA-
TYPES (UF 22180).







BULLETIN FLORIDA STATE


pallial oviduct


anterior pallial
oviduct -


oviduct II-


seminal


bursa


oviduct


oviduct I


1mm


FIGURE 1O.-Marstonia ogmorhaphe new species: (A) female reproductive system; (B) oviduct and
associated structures freed from the pallial oviduct; gpd = gonopericardial duct.


MUSEUM


Vol. 21, No. 3







1977 THOMPSON: SNAIL GENUS MARSTONIA 143














B \---


1mm


vas


penis


'vas deferens I imm

FIGURE 11.-Marstonia ogmorhaphe new species: (A) verge, lateral surface; (B) verge, mesad
surface; (C) male reproductive system.






BULLETIN FLORIDA STATE MUSEUM


A B


C D


Imm

FIGURE 12.-Marstonia pachyta new species: (A, B) HOLOTYPE (UF 22222); (C-E) PARA-
TYPES (UF 22228).


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


I 1mm

FIGURE 13.-Marstonia pachyta new species. Verges of two males from the type locality.


1977






BULLETIN FLORIDA STATE MUSEUM


A B


C D


Imm

FIGURE 14.-Marstonia olivacea (Pilsbry): (A-D) PARATYPES (ANSP 65460).


Vol. 21, No. 3










THOMPSON: SNAIL GENUS MARSTONIA


.
.





,.A.t
.
K

~>






BULLETIN FLORIDA STATE MUSEUM


A B C


, imm D E F
FIGURE 16.-Marstonia lustrica (Pilsbry): (A-F) lake, Newaygo Co., Michigan (UF 22190); (G-J)
Cedar Swamp, Champaigne Co., Ohio (UF 22223); (K-N) Turkeyfoot Lake, Summit Co., Ohio
(UF 22225).


Vol. 21, No. 3







1977 THOMPSON: SNAIL GENUS MARSTONIA 149


H I


Imm








BULLETIN FLORIDA STATE MUSEUM


1mm I D

FIGURE 17.-Marstonia halcyon new species: (A, B) HOLOTYPE (UF 22312); (C-E) PARATYPES
(UF 22311).


Vol. 21, No. 3







THOMPSON: SNAIL GENUS MARSTONIA


posterior pallial
- oviduct


anterior pallial
oviduct -



oviduct I-













oviduct II-


-bursa copulatrix

seminal receptacle


oviduct I


B

1mm


FIGURE 18.-Marstonia halcyon new species: (A) female reproductive system intact except for
the ovary; gpd = gonopericardial duct, sr= seminal receptacle; (B) oviduct and associated struc-
tures freed from the pallial oviduct.







BULLETIN FLORIDA STATE MUSEUM


0.5 mm


body.wall


apical gland


vas deferens II


vas deferens I


0.5 mm
II


FIGURE 19.--Marstonia halcyon new species: (A) lateral view of verge; (B) mesad view of verge;
(C) male reproductive system exclusive of the testis.


Vol. 21, No. 3






THOMPSON: SNAIL GENUS MARSTONIA


e halcyon Aagarhecta N castor

FIGURE 20.-The geographic distribution of Marstonia in the southeast coastal drainages.






BULLETIN FLORIDA STATE MUSEUM


A B


C D


Imm

FIGURE 21.-Marstonia castor new species: (A, B) HOLOTYPE (UF 22176); (C, D) PARATYPES
(UF 22177).


Vol. 21, No. 3






THOMPSON: SNAIL GENUS MARSTONIA


Bx


FIGURE 22.-Marstonia castor new species. Verge of male: (A) lateral surface; (B) mesad surface.







BULLETIN FLORIDA STATE MUSEUM


A B


C D


1mm

FIGURE 23.-Marstonia agarhecta Thompson: (A, B) HOLOTYPE (UF 20528); (C, D) PARA-
TYPES (UF 20529).


Vol. 21, No. 3







1977


FIGURE 24.-Marstonia agarhecta Thompson. Verge of male: (A) lateral surface; (B) mesad surface.


THOMPSON: SNAIL GENUS MARSTONIA







BULLETIN FLORIDA STATE MUSEUM


A

1mm


D

1mm


1mm


C

Imm


r1mm


E

1mm .


Imm


H

Imm


FIGURE 25.-Marstonia opercula: (A) M. lustrica (Pilsbry); (B) Nl. arga new species; (C) M. og-
morhaphe new species; (D) M. pachyta new species; (E) M. castor new species; (F) Al. olicacea
(Pilsbry); (G) AM. halcyon new species; (H) M. agarhecta Thompson.


Vol. 21, No. 3




















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