Front Cover
 Table of Contents
 Relationships of Hendersoniell...
 Hendersoniella lux n. sp
 Hendersoniella lux chonomphix n....
 Hendersoniella christmani...
 Literature cited
 Back Cover

Group Title: Bulletin of the Florida Museum of Natural History
Title: Mexican land snails of the genus Hendersoniella
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00095826/00001
 Material Information
Title: Mexican land snails of the genus Hendersoniella
Series Title: Bulletin - Florida Museum of Natural History ; volume 36, number 1
Physical Description: 23 p. : ill. ; 23 cm.
Language: English
Creator: Thompson, Fred G ( Fred Gilbert ), 1934-
Correa S., Alfonso
Florida Museum of Natural History
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1991
Copyright Date: 1991
Subject: Snails -- Classification -- Mexico   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Spatial Coverage: Mexico
Bibliography: Includes bibliographical references (p. 17).
General Note: Cover title.
General Note: Abstract in English and Spanish.
Statement of Responsibility: Fred G. Thompson and Alfonso Correa S.
 Record Information
Bibliographic ID: UF00095826
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 - 24638604

Table of Contents
    Front Cover
        Page i
        Page ii
        Page 1
    Table of Contents
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
    Relationships of Hendersoniella
        Page 8
        Page 9
        Page 10
    Hendersoniella lux n. sp
        Page 11
        Page 12
    Hendersoniella lux chonomphix n. ssp
        Page 13
    Hendersoniella christmani n. sp
        Page 14
        Page 15
        Page 16
    Literature cited
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
    Back Cover
        Page 25
Full Text

SI i i I


Fred G. Thompson and Alfonso Correa S.

Biological Sciences, Volume 36, Number 1, pp. 1-23 1991



BIOLOGICAL SCIENCES, are published at irregular intervals. Volumes contain about 300
pages and are not necessarily completed in any one calendar year.


Communications concerning purchase or exchange of the publications and all manuscripts should
be addressed to: Managing Editor, Bulletin; Florida Museum of Natural History; University of
Florida; Gainesville FL 32611-2035; U.S.A.

This public document was promulgated at an annual cost of $1197.70 OR
$1.197 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.

ISSN: 0071-6154


Publication date: May 23, 1991

Price: $1.25



Fred G. Thompson and Alfonso Correa S.*


The taxonomy of the genus is revised. Four species and subspecies are recognized: H.
palmeri (Dall, 1905), H. hlx new species, H. hl lux new subspecies, H. 1. choonomphix new
subspecies and H. christmani new species. H. panleri simplex Pilsbry, 1953 is synonymized with
H. palmcri. Hendersoniella is most closely related to Holospira on the basis of-shell characters
and soft anatomical features. The shell is discoidal in shape, not cylindrical, in contrast to other
genera of the Holospirinae. This is an adaptation for living in narrow crevices under spalding
surfaces of limestone boulders. The species are obligate calcicoles. The genus occurs over a
large area of eastern Mdxico in the states of Nuevo Leon and San Luis Potosi.

KEY WORDS: Land snails, Gastropoda, Urocoptidae, Holospirinae, Hendersoniella,
systematics, biogeography, M6xico, San Luis Potosi, Nuevo Leon, obligate calcicole.


La taxonomia de g6nero esta revisada. Cuatro species y subespecies son reconocidas: H.
palmeri (Dall, 1905), ti. hlx nueva especie, II. lux lux nueva subespecie, H. 1. chonomphiv nueva
subespecie y H. christnani nueva especie. TH. palmer simplex Pilsbry, 1953 se consider sin6nimo
de H. palmer. Hendersoniella esti mis estrechamente relacionado con Holospira, en base a las
caracteristicas de su concha y la anatomia de sus parties blandas. La concha tiene forma discoidal
no cilindrica, en contrast con otros generos de Holospirinae. Esta es una adaptaci6n para vivir
en estrechas grietas debajo de superficies desprendidas en rocas calizas. Las species son
calcifilas obligadas. El g6nero se distribuye sobre una extensa region al Este de M6xico, en los
estados de Nuevo Le6n y San Luis Potosi.

*Dr. Thompson is Curator in Malacology at the Florida Museum of Natural History, University of Florida, Gainesville FL
32611-2035, USA. Sr. Correa is Biologo at the Instituto Tecnol6gico de Ciudad Victoria, Ciudad Victoria, Tamaulipas, M6xico.

Thompson, F.G., and A. Correa S. 1991. Mexican Land Snails of the Genus Hendersoniella.
Bull. Florida Mus. Nat. Hist., Biol. Sci. 36(1):1-23.



In tro d uctio n .............................................................................................................................................. 2
Acknowledgements.............................................. .............................................. 3
M ethod s ......................................................................................................................... .................. 3
Hendersoniella ............................................................. .... 4
D description of the A natom y........................................................................................................... 4
R relationships of H endersoniella......................................................................... .................... 8
H endersoniellapal eri (D all) ................................................................... ..................... 8
H endersoniella x n. sp........................................................................... .............................. 11
H endersoniella lux lux n. ssp.......................... .. .............................................................. 11
-Hendersoniella lux chonomphiv n. ssp................................................ 13
H endersoni la christm ani n. sp......................................................................... ..................... 14
L iteratu re C ited ....................................................................................................................................... 17


Hendersoniella are medium-sized land snails with a thin discoidal shell.
In this respect they contrast strongly with all other species in the Holospirinae
and the Urocoptidae, which have cylindrical shells. Until recently the genus
was thought to be monotypic and restricted to a very small area on the eastern
slope of the Mexican Plateau east of the city of San Luis Potosi. The east slope
of the plateau and the Sierra Madre Oriental cover a very large area of eastern
M6xico. The northern half of this area, in the states of Coahuila, Nuevo Le6n,
San Luis Potosf, Tamaulipas, and Quer6taro, contain numerous mountain
ranges of calcareous rocks, each highly suitable for diverse molluscan
assemblages. The molluscan fauna of this area remains poorly known. Thus, it
is not surprising that additional species of Hendersoniella have been
discovered, and that the genus is more widely distributed than had been
previously thought.
Hendersoniella occurs in northeastern M6xico in the states of Nuevo Le6n
and San Luis Potosf. Within this area it is found on limestone mountain ranges
at intermediate elevations of about 1300-2100 m in submesic oak-juniper
thickets and forests. Colonies apparently are sparce, and the species seldom
are collected. The snails are highly specialized to retreat under the spalding
caps of huge limestone boulders and outcrops and deep within limestone
crevices. Seldom are their shells found elsewhere. They have not been found
associated with other Holospirinae, although Holospira occurs throughout its
Hendersoniella are obligate inhabitants of limestone substrates (obligate
calcicoles). As is typical of the Holospirinae, populations are ecologically
restricted to particular limestone outcrops. They do not inhabit or readily


disperse across intervening alluvial basins and clay deposits, nor are they
uniformly distributed over seemingly suitable limestone substrates. Such
isolation favors local speciation, and small distances between colonies can be
manifested in great differences in shell morphology.
Recent field work in San Luis Potosi and in Nuevo Le6n have brought to
light two new species of Hendersoniella. One is represented by two subspecies.
Another species also was discovered in southeastern San Luis Potosi near the
Quer6taro border (27018'N, 99005'W), but the material is unsatisfactory for
taxonomic treatment.


We wish to thank the following people who have assisted us in this study. The line
drawings comprising Figures 12-22 were produced by Wendy B. Zomlefer. Sharon W. Keeling
assisted with the arrangement of the illustrations. Steven P. Christman, Tallahassee, Florida,
provided diligent and cheerful assistance in the field. Kenneth C. Emberton, Academy of Natural
Sciences of Philadelphia (ANSP), Robert Hershler, National Museum of Natural History
(USNM), and Walter B. Miller, Tucson, Arizona, loaned important specimens essential to this
project. The junior author was able to conduct research at the University of Florida in 1990
through assistance provided by Ing. Jos6 Alfredo Gonzalez de Le6n, Instituto Tecnol6gico de Cd.
Victoria, and the Consejo Nacional de Ciencia y Tecnologia (CONACYT), M6xico. We are
grateful to all for their assistance.


Hendersoniella differ in shell shape from other Holospirinae because of
their discoidal shape. With cyclindical species, such as other holospirines, the
aperture may be attached to the previous whorl or it may project free on a
short neck. The neck may also be deflected laterally. The degree to which the
aperture may be forward projected or laterally deflected is highly variable
within even small samples. Conventionally the width of such shells is taken as
the width of the spire and does not include modifications of the last whorl
associated with the aperture. This contrasts with the convention used for
measuring most helicoid or discoid snails where the deflection of the last whorl
and aperture is incorporated in the width measurement. Hendersoniella
resembles other holospirines in the variability associated with the aperture
projection. Thus, the conventional methods for measuring cylindrical shells
are used in this study. Most holospirines, as well as the vast majority of other
cylindrical snails, have an imperforate or narrowly perforate base. A distinct
umbilicus usually is lacking, and seldom is the width of the perforation useful
for comparative purposes. Hendersoniella differs from other holospirines in
this feature, and various umbilical parameters yield useful measurements.


Measurements were made with an ocular micrometer through a WILD
M50 dissecting microscope. The height of the shell (H) is from the base to the
apex and does not include the aperture projection. The width of the shell (W)
is the greatest diameter across the apex posterior to the deflection of the
aperture. The umbilical width (Um) is along this same line from within the
inside suture of the last whorl that forms the umbilicus periphery. Most
population samples have a rounded base on the last whorl, and other
measurements of the umbilicus become highly arbitrary. The H/Um ratio is
based on the dimensions as defined here. This ratio is a function, in part, of
the depth of the umbilicus, and it helps to differentiate two species. Specimens
for dissection were removed from the shell by dissolving them in Bouins
Solution. Dissections were made in 70% ethanol.

Hendersoniella Dall, 1905

Hendersonia Dall, 1905; Smiths. Misc. Coll., 48: 187. Type species: Hendersonia palmer Dall,
1905. Non Hendersonia A. J. Wagner, 1905 (Gastropoda, Prosobranchia).
Hendersoniella Dall, 1905; Proc. Biol. Soc. Wash., 18: 189. Bartsch, 1906; Proc. U. S. Nat. Mus.,
31: 153-155. Type species: Hendersonia palmeri Dall, 1905.

Diagnosis.-- Holospirinae with a discoidal shell, consisting of about 7-9
whorls. Apical 1.5 whorls nipple-shaped and smooth. Sculpture of following
whorls consisting of growth striations. Aperture projecting free from last
whorl and turned dorsally to about the level of the dorsal surface of the shell.
Peristome reflected. Aperture narrowly pear-shaped with the parietal margin
indented by a weak lamellar tubercle. Interior of shell with a parietal lamella.
The lamella, when present, can easily be seen by immersing fresh shells in
toluene or xylene, which renders the shell partially transparent.


We examined anatomical material of Hendersoniella palmer, H. 1. lux n.
sp. and H. christmani n. sp. Five specimens of each were dissected. The
following descriptions are based on H. 1. lux. Differences for the other species
are noted.

Pallial organs (Fig. 1).-- Pulmonary cavity extending about 1 1/8 whorls
posterior to mantle collar. Kidney long and sigmoid, about 1/7 the length of
the lung. Primary ureter short and recurved around anterior end of kidney. A






Figures 1, 2. Hendersoniella 1. lux n. sp. Fig. 1, Pallial organs: arrow indicated longitudinal axis of
lung. Scale = 2 mm. Fig. 2, jaw. Scale = 1 mm.

closed secondary (descending) ureter is absent. Heart about 3/4 the length of
the kidney. Ventricle slightly longer than the auricle. Pulmonary vein
unbranched to near mantle collar, where it receives numerous fine veinules
that are transverse to the surface of the lung and perpendicular to the
pulmonary vein.

Digestive system.-- Jaw (Fig. 2). Solid, arcuate with a wide medium
projection below; hyaline, face with very fine diverging vertical striations from
wear on front; lacking ribs on the outer surface. Radula (three specimens of
each examined). Typical for Holospirinae. Transverse rows arranged in a
depressed W-formation. Central tooth unicuspid with a broad lanceolate
mesocone. Lateral teeth 4-6, unicuspid and about equal to the central tooth in
size and shape. Marginal teeth 13-17; marginals polycuspid with both the
entocones and the ectocones subdividing on the outermost teeth. Differences
in the numbers of lateral teeth and marginal teeth are given in each of the




, I






.y -3 .4 V -

Figures 3, 4. Reproductive anatomy of Hendersoniella lux lux new species. Scale for 3 = 4 mm;
scale for 4 = 2 mm.


species descriptions. Esophagus long and slender, without bulbous
enlargement. Salivary gland on long ducts; forming a mat that covers dorsal
surface of anterior esophagus. Stomach uniformly thin-walled. Intestinal loop
short, reaching middle of intestinal crop. Anus opening at mantle collar.

Reproductive system (Figs. 3, 4).-- Genital atrium very short and stocky.
Penis sheath absent. Spermathecal duct very long and slender; originating
from genital atrium at junction with vagina; spermatheca extending beyond
kidney to anterior 1/4 of albumen gland; spermatheca slightly enlarged in
diameter, elongate club-shaped. No diverticulum present. Albumen gland 3/8
whorls in length, lying along dorsal side of coelom posterior to pulmonary
cavity; posterior end terminating at about 1.5 whorls behind mantle collar.
Albumen gland long, slender; posterior loop of intestine forming a sigmoid
groove on dorsal surface of anterior half. Hermaphroditic duct (not
illustrated) lying along baso-columellar wall of digestive gland; entering
albumen gland just above uterus. Talon (FPSC complex) ovate in shape;
completely exposed; covered with a thin veil of black pigmented tissue as is
also the base of the hermaphroditic duct. Seminal receptacle simple, thick-
walled and club-shaped. Fertilization pouch thin-walled, saccular. Vagina very
long and slender; thin walled and without clear indication of internal papillae
or folds. Penis (Fig. 4) long and slender; interior smooth; without conspicuous
folds or papillae. Epiphallus long and slender; demarcated from penis by a
slight internal constriction; interior with 4-6 longitudinal folds. Vas deferens
demarcated from epiphallus internally by lining of papillae. Flagellum and
caecum absent. Penis retractor muscle originating on middle of epiphallus;
relatively stout and short; attaching to dorsad inner wall of lung about 1/4 of
whorl behind mantle collar.
The dissected specimens of Hendersoniella palmer (ANSP 164173) were
collected by Pilsbry in 1934 from near the type locality. The reproductive
system is similar to that of H. 1. lux in essential characteristics.
In Hendersoniella christmani the reproductive anatomy is similar to that
of H. 1. lux, except as follows. The spermatheca is more ovate in shape and lies
at the base of the albumen gland. The penis retractor muscle is highly variable
in length and inserts on the middle of the pallial cavity wall.

Retractor muscle system.-- The retractor muscles are alike in the three
species. Retractor muscles forming a sheath along ventro-columellar side of
body and extending about 3.5 whorls posteriorly from mantle collar and
attaching to mantle; no apparent connection to shell. Columellar retractor
very long and slender, subdividing into a right and a left pedal retractor and a
pharyngeal retractor. Right ocular retractor originating from right pedal
retractor and passing between pharynx and genital atrium, not passing through
angle between penis and vagina as in Bostrichocentnum (Thompson 1964). Left


ocular retractor originating from left pedal retractor. Pharyngeal retractor
divided into four equal slips that attach to base of pharynx, and a slightly wider
dorsal slip that attaches to posterior end of pharynx.


The basic internal shell structure in the Holospirinae consists of four
lamellae within the last whorl, the columellar, parietal, palatal, and basal
lamellae. This is the typical arrangement in Holospira. Various of these
lamellae are lost in different genera and subgenera, and similar internal shell
structures appear to have evolved independently within the subfamily. The
single lamella of Hendersoniella is homologous in position and function to the
parietal lamella in Holospira (also referred to as the superior lamella). It
impresses into the right side of the snail's body to partially separate the
intestine from the rest of the pallial cavity. Hendersoniella is unique within the
subfamily by possessing only a parietal lamella.
The anatomy of the Holospirinae is very poorly known, and most intra-
generic comparisons are not possible at present. Reviews for anatomically
known genera are given in Thompson (1964 1976). Among the genera for
which data are available the anatomy of Hendersoniella differs but little from
that of Holospira (Pilsbry 1903). The reproductive system is most similar to
Holospira sensu stricto by lacking a diverticulum (appendix) on the
spermathecal duct. It differs from Holospira, as well as most other
Holospirinae, by having a very long slender penis, as opposed to a short,
bulbous penis. Epirobia is similar in penis morphology, but differs by having a
long flagellum at the end of the penis, and by having a diverticulum on the
spermathecal duct. The location of the right ocular retractor muscle is unique
within the Holospirinae, as far as is known. In Hendersoniella the muscle
passes between the pharynx and the genital atrium. In other genera
(Coelostemma, Holospira, Bostrichocentnmn, Epirobia) the right occular
retractor passes through the genital atrium between the penis and the
spermathecal duct. Other aspects of the soft anatomy, including the jaw and
radula, are similar to Holospira but are non-conclusive.

Hendersoniella palmnei (Dall, 1905)

Hendersoniapahneri Dall, 1905; Smiths. Misc. Coll., (1590): 187-190; pl. 48, figs. 1-4.
Hendersoniellapabneri (Dall, 1905). Dall, 1905; Smiths. Misc. Coll., 18: 189. Bartsch, 1906; Proc.
U. S. Nat. Mus., 31: 153-155; text figs. 13-16; pl. 5, figs. 1-4. Pilsbry, 1953; Proc. Acad.
Nat. Sci. Phila., 105: 160.
Hendersoniellapalmeri simplex Pilsbry, 1953; Proc. Acad. Nat. Sci. Phila., 105: 160.


Diagnosis.-- The shell is discoidal with a flat dorsal surface and an H/W
ratio of 0.23-0.27. The periphery is acutely carinate with the carina lying above
the middle of the whorl. The parietal lamella, when present, is about 1/8
whorl long and extends only about halfway across the lumen of the whorl. The
umbilicus is shallow and concave with an H/Um ratio of 0.32-0.45; it is dish-
shaped, not funnel-shaped as in other species. The aperture projects
dorsolaterally on a short neck and is narrowly pear-shaped. The radula has 6
lateral teeth and 16 marginal teeth on each side.

Shell (Figs. 5-11).-- Discoidal, about 9-10 mm wide, about 0.21-0.26 times
as high as wide. Shell consisting of about 8.1-8.8 whorls. Sculpture consisting
of irregular incremental striations that become more strongly developed as
coarse riblets on the neck of the aperture.
Apical whorl raised. Body whorl with a sharp peripheral keel that lies
above the middle of the whorl. Body whorl strongly convex above the keel,
concave and then flattened below the keel and obtusely rounded on the base.
Aperture projecting upward between level of periphery and apex; neck directed
dorsolaterally, relatively short, with a strongly impressed longitudinal furrow
on dorsal side posterior to parietal tubercle of peristome. Neck semi-lunar in
cross-section. Plane of aperture slightly oblique to dorsal surface of shell.
Longitudinal axis of aperture tangential to periphery of shell disc (Fig. 9, 14).
Umbilicus broad and dish-shaped; 0.59-0.63 times the width of the shell (Fig. 6,
10, 16). Height of the shell usually 0.32-0.42 times the width of the umbilicus.
Interior of body whorl with a parietal lamella that lies about 1/8 of a whorl
behind the aperture (Fig. 8). The lamella is about 1/8 of a whorl in length, and
projects outward nearly perpendicular to the inner wall and about halfway
across the lumen of the whorl toward the peripheral keel (Fig. 21). The
lamella is highest in its mid-section and is slightly oblique so that its anterior
end converges toward the umbilicus. Its outer edge is thickened and cord-like.
Three samples of Hendersoniella palmer are available. The type series
(USNM 110385) consists of six specimens, two of which are immature. A
second series, collected by H. A. Pilsbry in the immediate vicinity of the type
locality (ANSP 164173), consists of 47 adults and many juveniles. In addition
we examined 20 adult shells of the type series of the form described as H.
palmer simplex. Measurements for these three lots are summarized in Table

Type localities.-- H. palmeri: SAN LUIS POTOSif Alvarez Mountains.
HOLOTYPE: USNM 110385 + 5 paratypes. H. p. sinplex: SAN LUIS
POTOSI, Alvarez, in crevices and under stones in a very rocky pasture north of
the railroad, 7400 ft alt. Alvarez (22001'53"N, 100036'41"W) is located in a
valley east of the Sierra de Alvarez, and is about 4 km by road south of San


Table 1. Shell measurements in mm of three population samples ofHendersoniella palmeri (Dall,
1905). H = height, W = width, Um = umbilicus, Wh = whorls.

H W Um Wh H/W Um/W H/Um

USNM 110385, type series ofpanleri

holotype 2.3 8.9 5.6 8.7 0.26 0.61 0.41
paratype 2.3 9.1 5.6 8.5 0.25 0.62 0.41
paratype 2.4 9.6 6.0 8.7 0.25 0.62 0.40
paratype 2.6 9.5 5.8 8.8 0.27 0.61 0.45

ANSP 164173 (n=43)

Mean 2.2 9.9 6.0 8.4 0.23 0.61 0.37
S 0.10 0.36 0.29 0.26 0.02 0.02 0.02
min. 2.1 9.4 5.5 8.1 0.20 0.59 0.32
max. 2.3 10.3 6.5 8.7 0.25 0.64 0.42

ANSP 164313, type series of simplex (N= 20)

Mean 2.2 9.4 5.6 8.1 0.23 0.59 0.39
S 0.11 0.32 0.30 0.21 0.02 0.01 0.03
min. 2.0 8.9 5.1 7.9 0.21 0.57 0.34
max. 2.3 10.1 6.1 8.3 0.26 0.62 0.44

Francisco. HOLOTYPE: ANSP 164312. PARATYPES: ANSP 164313 (20
adult and 13 juvenile shells).

Other specimens examined.-- SAN LUIS POTOSI: Alvarez, hill north of
the railroad at a large quarry; 8000 ft alt. (ANSP 164173, 47 shells, 10
preserved specimens).

Distribution.-- Known only from the immediate vicinity of Alvarez, San
Luis Potosi.

Remarks.-- The specimens comprising the type series (USNM 110385)
and the series from near Alvarez collected by H. A. Pilsbry (ANSP 164173)
differ in their measurements and in the projection of the aperture (Figs. 5-7, 8-
11). Almost certainly they came from different populations. Among the
populations from near Alvarez, Pilsbry (1953) recognized two subspecies based
on the presence or absence of the parietal lamella. The two forms do not
differ in other features. The form described as simplex was differentiated by
the absence of the lamella, although Pilsbry noted that in two specimens of ten
that were opened the lamella was weakly developed. Of twenty adult shells in
the paratype series (ANSP 164313), three have a weakly developed lamella.


The lamella occupies the same position as occurs in the typical form. Of 47
adult specimens of another sample (ANSP 164173), seven lack a lamella. In
light of the variation of this structure in populations from near Alvarez we feel
that taxonomic recognition of H. palmer simplex is not warranted.

Hendersoniella lux new species

Diagnosis.-- A species of Hendersoniella characterized by having a broad
funnel-shaped umbilicus that has an H/Um ratio of 0.40-0.63. The shell has a
low dome-shaped spire with an H/W ratio of 0.23-0.34, and an acutely carinate
periphery with the carina lying above the middle of the whorl. The aperture is
directed upward on a relatively long neck and is broadly pear-shaped. The
radula has 4 lateral teeth and 17 marginal teeth on each side.
This species is closely related to Hendersoniella palmer. It differs from
the latter by its more funnel-shaped umbilicus, by its dome-shaped spire, by its
more dorsally extended and broader aperture, by its much longer and higher
parietal lamella, and by having 4 as opposed to 6 lateral teeth in the radula.
Two subspecies are recognized. The nominate subspecies has a long
parietal lamella situated within the last half whorl. The second subspecies
lacks a lamella and also differs by other features of the shell.

Hendersoniella lux lux new subspecies

Diagnosis.-- The shell has a long parietal lamella that is about a half
whorl in length and extends across the lumen of the whorl almost to the
opposite side. The base of the last whorl is narrow but rounded. The
periphery is strongly keeled with a concave furrow beneath it. The umbilical
wall of the whorls tend to be rounded so that the umbilicus is not flat-sided as
in the following subspecies. The neck of the aperture is long and is directed

Description.-- Shell (Figs. 23-26) containing 8.3-9.3 whorls; 0.23-0.33
times as high as wide. Sculpture consisting of fine incremental striations that
are equally developed on the base and spire, but become irregularly spaced
coarse riblets on the neck of the last whorl. Spire low dome-shaped with apical
1.5 whorls forming a low nipple. Periphery of last whorl strongly carinate
above middle of whorl; last whorl with dorsal surface strongly convex above
carina; side obliquely flattened and weakly concave below carina, and base
subcarinate or rounded. Aperture extended above the apex on a relatively long


neck. Neck hemispherical in cross-section; flattened dorsally with a
conspicuous dorsal longitudinal furrow that continues to parietal tubercle.
Aperture more broadly pear-shaped than in H. palmed; longitudinal axis of
aperture tangential to periphery of disc (Figs. 12, 23). Umbilicus broadly
funnel-shaped (Fig. 7); outer perimeter formed by last whorl; umbilicus 0.53-
0.60 times width of shell; height of shell 0.41-0.60 times width of umbilicus.
Interior of last whorl with a high parietal lamella that projects nearly to the
opposite wall below the peripheral angle (Figs. 22, 26); middle of the lamella
separated from opposite wall by a gap of about 0.1 mm; lamella originating
about 1/8 whorl behind neck of aperture and is about 1/4-1/2 whorl in length;
sloping downward at its anterior end; arched downward in the middle and
conspicuously thickened along its edge. Lamella present in all adult specimens
Measurements based on 49 adult specimens are summarized in Table 2.
Radula (3 specimens) with 4 laterals and 17 marginals on each side.

Type locality.-- SAN LUIS POTOSI, Valle de Las Fantasmas, 22 km west
of Santa Catarina (22003'34"N, 100033'16"W); 2150 m alt. Santa Catarina is a
village on the road from Rio Verde to the city of San Luis Potosi, and is 29 km
east of San Francisco. The Valle de Las Fantasmas is on the east slope of the
plateau between San Luis Potosi and Rio Verde. The valley received its name
from numerous grotesque rock formations that were sculpted by the weather
over eons. Most of these formations have been destroyed by small-scale

Table 2.- Measurements in mm of Hendersoniella hlx hux new subspecies (UF 145385) and
Hendersoniella lru chonomphix new subspecies (UF 143586). H = height, W = width, Um =
umbilicus, Wh = Whorls.

H W Um Wh H/W Um/W H/Um

hix (n = 47)

holotype 2.6 9.3 5.3 8.6 0.28 0.60 0.49
Mean 2.6 9.6 5.4 8.8 0.27 0.57 0.48
S 0.26 0.39 0.26 0.29 0.03 0.03 0.05
min. 2.3 9.3 5.0 8.3 0.23 0.53 0.41
max. 3.1 10.3 6.0 9.3 0.33 0.60 0.60

chonomphix (n = 31)

holotype 3.1 9.0 4.8 8.3 0.34 0.53 0.65
Mean 2.7 9.4 5.2 8.1 0.29 0.55 0.52
S 0.28 0.40 0.39 0.24 0.03 0.03 0.07
min. 2.4 8.8 4.8 7.6 0.23 0.52 0.40
max. 3.1 10.3 6.0 8.3 0.34 0.62 0.63


quarry operations during the last twenty years so that little remains to indicate
the origin of the name. The area of the type locality is in a mesic oak forest
with occasional junipers. Live snails were found aestivating in narrow crevices
in limestone boulders. HOLOTYPE: UF 165719; collected 2 April 1965 by
Fred G. Thompson. PARATYPES: UF 143585 (31), Museo Nacional de
M6xico (5), Instituto Tecnol6gico Cd. Victoria, ITCVZ 105 (5), Walter B.
Miller Collection (5); same data as the holotype. In addition we dissected five
specimens from the type series preserved in alcohol.

Distribution.-- This subspecies is known only from the immediate vicinity
of the type locality. It was also collected at a station 23 km W of Santa
Catarina (22003'23"N, 100033'28"W); 2300 m alt (UF 143583).

Remarks.-- The relationship of this subspecies within the genus is
discussed below.

Etymology.-- The name hex is from the Latin, hlx (f.), a light, referring to
the lamp-shape of the shell.

Hendersoniella htx chonomphix new subspecies

Diagnosis.-- The shell is similar to H. 1. hix except that it has an average
of fewer whorls, it lacks an internal lamella, the periphery of the last whorl is
sharply keeled and overhangs a shallow furrow, and the base is sharply keeled.
The umbilicus is flat-sided, whereas in hux the whorls tend to be rounded along
the umbilical wall. The neck of chonomphix is shorter and is more laterally

Description.-- Shell (Figs. 27-29) with 7.6-8.8 whorls. Low dome-shaped
with the apical 1.5 whorls forming a nipple. Shell 0.23-0.34 times as high as
wide. Sculpture similar to that of H. 1. lux. Last whorl with a strong peripheral
keel; weakly arched above keel; distinctly furrowed below keel; side of whorl
flat below furrow. Umbilicus deep and sharply defined by a basal keel (Figs.
18, 29). Umbilical wall nearly flat-sided; umbilicus 0.53-0.62 times as wide as
shell; height of shell 0.40-0.63 times width of umbilicus. Aperture with a
moderately long neck that extends dorsolaterally to about halfway between the
periphery and the apex; neck hemispherical in cross-section; dorsal surface of
neck flattened with a strongly impressed longitudinal furrow extending to
peristome tubercle. Plane of aperture lying at about 30 to plane of shell.
Aperture broadly pear-shaped with its longitudinal axis tangential to periphery
of shell (Fig. 13). Interior of shell lacking lamella.


Thirty-one adults from the type series were examined. Eight were opened
or had perforations that permitted the interior to be viewed for the presence of
a parietal lamella. The others were immersed in toluene to render the shell
transparent. None showed a trace of a lamella.
Measurements for the type series are given in Table 2.
Radula not examined.

Type locality.-- SAN LUIS POTOSI, Valle de Las Fantasmas, hillside
15.5 km west of Santa Catarina, (22004'01"N, 10031'44"W); 1770 m alt. The
area of the type locality is in a dry oak-juniper forest. Snails were crawling on
limestone outcrops during a late afternoon misty rain. HOLOTYPE: UF
166310; collected 19 September 1967 by Fred G. Thompson. PARATYPES:
UF 143586 (22), Museo Nacional de M6xico (5), Instituto Tecnol6gico Cd.
Victoria, ITCVZ 106 (5); same data as the holotype.

Distribution.-- Known for certain only from the type locality. A series of
7 specimens from the "Valle de Fantasmas" (UF 92981), collected by a
speleological expedition in 1983, is not accompanied by more precise

Remarks.-- The relationship of this subspecies to Hendersoniella htx htx
suggests a similarity to that between simplex and H. palmer. However, this is
not the case. We regard chonomphix as a taxon distinct from htx; chonomphix
consistently lacks a parietal lamella whereas lux consistently possesses the
lamella. Other characteristics of the shell, such as the projection of the
aperture, the structure of the umbilicus and the presence or absence of a basal
keel on the last whorl also warrant taxonomic separation. This degree of
differentiation does not occur between simplex and pahneri. A strong
argument could be made for recognizing htx and chonomphix as distinct
species on the basis of these differences. Additional samples from this area of
San Luis Potosi are needed to clarify the relationship between the two.

Etymology.-- The name chonomphix is from the Classical Greek choane, a
funnel, and omphalos, an umbilicus, in allusion to the funnel-shaped umbilicus
characteristic of this subspecies.

Hendersoniella christmani new species

Diagnosis.-- The shell is low dome-shaped with a raised apical whorl.
The periphery is obtusely angulate at the base. The aperture is deflected
dorsally on a long neck. The greatest length of the aperture is on an axis that


passes across the top of the shell, not tangential to the disc as in other species.
The umbilicus is confined within the antipenultimate whorl and is about 1/3
the width of the shell. The parietal lamella is 1/2-5/8 whorls in length and is
deeply immersed within the last whorl. Radula with four lateral teeth.

Description.-- Shell (Figs. 30-34) discoidal with a low dome-shaped spire;
shell about 0.23-0.30 times as high as wide; consisting of about 8.6-9.6 whorls.
Sculpture consisting of coarse and numerous incremental striations that are
stronger on the base than on the spire and increase as thread-riblets on the
ventral side of the neck. Periphery obtusely angulate, lying nearly at the base
of the last whorl; outer side of whorls nearly flattened; rounded dorsally with a
moderately impressed suture. Base flat; outermost 3 whorls of base planular
with umbilicus circumscribed by antipenultimate whorl. Umbilicus deep and
thimble-shaped; 0.33-0.39 times the width of the shell (Figs. 19, 31). Neck of
last whorl deflected upward so that the aperture is raised to or above apex;
neck triangular in cross section; without a longitudinal impressed dorsal
furrow. Aperture auriculate in shape with it greatest length nearly aligned
across the center of the shell (Figs, 15, 30). Parietal lamella (Figs. 33, 34) 1/2-
5/8 whorls long; deeply immersed, anterior end terminating 3/4 whorls behind
aperture; anterior end lowest, lying below middle of parietal wall, directed
outward toward opposite wall; lamella ascending inward along parietal wall
with its edge arched upward along the posterior half so that it almost touches
the dorsal wall of the whorl (Fig. 20).
Seven adult shells comprise the type series. One was opened to
determine the size and course of the parietal lamella (Fig. 33); six others were
cleared in toluene, and they conform very closely with the opened specimen.
Measurements are given in Table 3.
Radula with 4 lateral teeth and 13 marginal teeth on each side.

Type locality.-- NUEVO LEON, Municipio Santiago, limestone hillside
on south side of Arroyo San Juan, 2.5 km west-northwest of La Ci6nega,
25022'34"N, 1000014'55"W; 1350 m alt. La Ci6nega lies in a deep canyon at the
fork of the Arroyo San Juan and a smaller arroyo from the east just before
they enter the Cafion San Crist6bal. For most of the year the river is dry or
has intermittent seeps. The valley is bordered on the north side by the high
limestone cliffs of the Sierra de San Crist6bal and to the south by steep
limestone hills and bluffs. The type locality is to the west of La Ci6nega where
the road passes between a low limestone hill and the south bank of the river.
The hillside was covered by the thicket of small oaks and shrubs. Live snails
were found under limestone slabs that were spalding from the underlying rock.
HOLOTYPE: UF 166309; collected 26 December 1989 by Steven P.
Christman. PARATYPES: UF 159249 (6); same data as the holotype. Five
additional specimens from the type locality were preserved for dissection.


Table 3. Measurements in mm of three population samples of Hendersoniella christmani new
species. H = height, W = width, Um = umbilicus, Wh = whorls.

H W Um Wh H/W Um/W H/Um

Type Series

holotype 2.3 8.9 3.1 9.2 0.26 0.35 0.47
paratype 2.3 9.6 3.8 9.6 0.24 0.39 0.68
paratype 2.3 8.9 3.3 9.3 0.26 0.37 0.78
paratype 2.3 8.4 3.8 9.1 0.27 0.36 0.74
paratype 2.3 8.8 3.1 9.5 0.26 0.36 0.74
paratype 2.2 8.6 3.1 9.3 0.26 0.36 0.71
paratype 2.1 8.9 3.3 9.4 0.24 0.37 0.64

UF 159189 (n = 13)

Mean 2.2 8.2 2.9 9.1 0.27 0.35 0.77
S 0.14 0.52 0.16 0.19 0.02 0.01 0.07
min. 2.8 6.9 2.6 8.7 0.23 0.33 0.68
max. 2.4 8.6 3.1 9.4 0.30 0.38 0.88

UF 126730 (n = 18)

Mean 2.1 7.6 2.6 8.9 0.28 0.34 0.89
S 0.14 0.34 0.19 0.15 0.02 0.02 0.11
min. 2.8 7.0 2.3 8.6 0.25 0.31 0.72
max. 2.4 8.5 2.9 9.1 0.32 0.35 1.16

Distribution.-- This species is known from dry valleys east-northeast of
Santiago. It was collected at two other stations in addition to the type locality.
NUEVO LEON: 2 km north of La Cienega (25022'09"N, 10014'15"W), 1350
m alt. (UF 159189); El Tejocote, 3.4 km ESE of Laguna de Sanchez,
(25019'54"N, 100014'56"W), 1920 m alt (UF 126730).

Remarks.-- This species is strikingly distinct from other Hendersoniella
because of the numerous differences in the shell as noted above in the
diagnosis. It is geographically separated from other known Hendersoniella by a
distance of about 400 km.
The two population samples from near La Ci6nega are alike in all
essential features. The two localities are on opposite sides of the Arroyo San
Juan, but regardless of this physical isolation, no significant differences are
apparent. The population from El Tejocote (UF 126730) is referred to H.
christmani with less certainty because of the less receded parietal lamella. In
the typical form from near La Ci6nega the anterior end of the parietal lamella
originates about 3/4 of a whorl posterior to the aperture (Fig. 33). The


Tejocote have the anterior end of the lamella originating about 1/2 of a whorl
posterior to the aperture (Fig. 34). The two forms do not differ in other salient
We hesitate to recognize the population from El Tejocote as
taxonomically distinct. No doubt many populations of Hendersoniella occur in
this region of southern Nuevo Le6n. Until geographic variation of this genus
in southern Nuevo Le6n is further investigated we favor recognizing only one
taxon in the region.

Etymology.-- This snail is named in honor of Steven P. Christman who
discovered, after much difficulty, the live specimens that comprise the type


Bartsch, P. 1906. The urocoptid mollusks from the mainland of America in the collection of the
United States National Museum. Proc. U. S. Natl. Mus. 31:109-160; pls. 3-5.
Dall, Wm. H. 1905. A new genus and several new species of landshells collected in central
M6xico by Doctor Edward Palmer. Smithsonian Misc. Coll. 48: 187-194; pls. 43-44.
Dall, Wm. H. 1905b. Note on the name Hendersonia. Proc. Biol. Soc. Washington 18:189.
Pilsbry, H. A. 1903. Manual of conchology, II. Vol. 15:1-323; pls. 1-65. Philadelphia.
Pilsbry, H. A. 1953. Inland Mollusca from northern M6xico. II. Urocoptidae, Pupillidae,
Strobilopsidae, Valloniidae and Cionellidae. Proc. Acad. Nat. Sci. Philadelphia 105:133-
167; pls. 3-10.
Thompson, F. G. 1964. Systematic studies on Mexican land snails of the genus Holospira,
subgenus Bostrichocentnum (Stylommatophora: Urocoptidae). Malacologia 24:131-143.
Thompson, F. G. 1976. The genus Epirobia in Chiapas, M6xico. Nautilus 90:41-46.




9 10

Figures 5-11. Hendersoniella palmer (Dall). Figs. 5-7, Holotype (USNM 110385); Figs. 8-11,
ANSP 164173.


Figures 12-15. Hendersoniella. Drawings of the aperture. Bars indicate direction of major axis
of the aperture. Fig. 12, H. lux hux n. sp. HOLOTYPE (UF 165719). Fig. 13, H. lux chonomphix
n. ssp. HOLOTYPE (UF 166310). Fig. 14, H.palmeri (Dall) HOLOTYPE (USNM 110385). Fig.
15, H. christmani n. sp. HOLOTYPE (UF 166309).


Figures 16-19. Hendersoniella. Cross-sections of shells showing configuration of umbilicus and
whorls. Fig. 16, H. palmer (Dall) (ANSP 164173). Fig. 17, H. 1. lux n. sp., PARATYPE (UF
143585). Fig. 18, H. 1. chonomphix n. ssp., PARATYPE (UF 143586). Fig. 19, H. christmani n. sp.
(UF 159189).


Figures 20-22. Hendersoniella. Shells partially opened to show curvature and projection of
parietal lamella. Fig. 20, H. christmani n. sp. (UF 159189). Fig. 21, H. palmeri (Dall) (ANSP
164173). Fig. 22, H. 1. lux n. sp. PARATYPE (UF 143585).




27 26

Figures 23-29. Hendersoniella lux n. sp. Figs. 23-25, H. 1. hux n. ssp. HOLOTYPE (UF 165719).
Fig. 26, PARATYPE (UF 143585). Figs. 27-29, H. 1. chonomphiv n. ssp. HOLOTYPE (UF


30 31

-.., S ^Q -q f

33 34

Figures 30-34. Hendersoniella christmani n. sp. Figs. 30-32, HOLOTYPE (UF 166309). Fig. 33,
PARATYPE (UF 159249). Fig. 34, El Tejocote (UF 126730).

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