BULLETIN
S. I

of the
FLORIDA STATE MUSEUM

Biological Sciences
Volume 31 1987 Number 2

A REVIEW OF THE LAND SNAILS OF MONA ISLAND,
WEST INDIES

FRED G. THOMPSON

=  A Pr

2,*91 + pir
UNIVERSITY OF FLORIDA GAINESVILLE



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A REVIEW OF THE LAND SNAILS

OF MONA ISLAND, WEST INDIES

FRED G. THOMPSON*

ABSTRACT

The fauna consists of 24 species and subspecies. Nine taxa are endemic to the
island, four are related to species on Puerto Rico, and three are related to species on
Hispaniola. The biogeographic relationships of two are less clear. Thirteen species are
regarded as introduced. The remaining nonendemic native species show mixed affinities
with Puerto Rican and Hispaniolan taxa.

The following new taxa are described from Mona Island: Stoastomops grada new
species, Varicella (Sigmataxis) nesiotes new species, Microceramus stenegrus new species,
Hoieda insularis eurytrema new subspecies, and PlaRioptycha musicola fortisculpta new
subspecies. Hoieda i. insularis new species is described from the satellite island of Monita.
The following is a new name combination: Drymaeus virgulatus beattvi for D. elonzatus
beattyi Clench

RESUMEN

La fauna de la Isla Mona consiste de 24 especies y subespecies. Nueve taxones
son enddmicos a la isla. Cuatro estan emparentados con especies de Puerto Rico y tres con
especies de Hispatiola. Las relaciones biogeograficas de dos de las especies no son muy
claras. Trece especies se consideran introducidas. Las restantes especies nativas no
enddmicas muestran afinidades tanto con taxones de Puerto Rico como de Hispafiola. Se
describen los siguientes taxones para la Isla Mona: Stoastomops grada nueva especie,
Varicella (Sigmataxis) nesiotes nueva especie, Microceramus stenegrus nueva especie,
Hoieda insularis eurytrema nueva subespecie, y Plagioptycha musicola fortisculpta nueva

*"rllc author is Curator iii Malacology at the Florida State Museum, University of Florida,
Gainesville FL 32611.

7HOMPSON, F.G. 1987. A Review of the Land Snails of Mona Island, West Indies. Bull.
Florida State Mus., Biol. Sci. 31(2):69-106.



70 BULL. FLORIDA SrATE MUS., BIOL. SCI. 31(2)

subespecie. La nueva subespecie, Hoieda i. insularis se describe para la isla sat61ite de
Monita. La siguiente es una nueva combinaci6n: Dr¥maeus virzulatus beattyi en vez de I2·
elonzatus beattyi Clench.

TABLE OF CONTENTS

INTRODUCrION 70
ACKNOWLEDGEMENTq 73
THE MOLLUSCAN FAUNA 73

Helicinidae 76
Annulariidae 81
Pupillidae 83
Cerionidae. 83
Helicarionidae 83
Ferussaciidae 83
Subulinifir. 84
Oleacinidae 84
Bulimulidae 87
Urocoptidae 89
Sagdidae 94
Polygyridae 101
Xanthonychidar 1A1

LITERATURE CITED 105

INTRODUCTION

In 1972 studies on the flora, fauna, and mineral resources of Mona
Island were initiated because of proposed economic developments and a
proposed national park on the island (Wadsworth 1975). I visited the island
for four days during May 1974 to survey the land snail fauna. A second visit
of three days was made during November 1978 for the same purpose. Both
visits were at the height of long dry periods, and only dead shells of most
species were found.

Mona Island lies in the Mona Passage about halfway between
Puerto Rico and Hispaniola at 18006'N, 67055'W. It is a small, bean-
sliaped desert island about 11 km long by 7 km wide. The island is capped
by the Miocene Lirio Limestone, which is rugged and dog-toothed. This
overlays the middle or lower Miocene Isla de Mona Dolomite (Aaron
1975). The island is bordered on all sides by abrupt cliffs that rise about 45



THOMPSON: MONA ISLAND LAND SNAILS 71

m high. The island is bounded along its southern and western sides by
narrow Holocene coastal plains that were inhabited by Taino Indians at the
time of Columbus. It has been inhabited intermittently by settlers since
then. Apparently the name of the island is derived from the Taino name
Amona and not from the Spanish mona, meaning monkey (Wadsworth
1975).

The island plateau is covered with a dense submesic scrub thorn
forest similar in floral composition to that of other low-lying limestone
islands in the West Indies (Woodbury 1975). This thorn forest contains
scattered patches of mesic high forest toward the center of the island and a
narrow fringe of low xeric scrub along the north and east edges of the
plateau. The coastal plains generally are covered with submesic thorn
forests. Along the southwestern base of the plateau, near Sardinero
(Station 3), grows a narrow fringe of wet evergreen forest fed by ground-
water seepage from the cliffs.

FIELD STATIONS

Mollusk collections were made at thirteen field stations (Fig. 1). A brief
description of each follows.

STATION 1. Slopes and bluff behind Sardinero, amid limestone boulders and
along cliff. Mesic forest.

SrATION 2. Base of Iimestone cliff at Sardinero in an area with a high mesic
forest.

STATION 3. Base of limestone cliff at Sardinero in high mesic forest with
patches of wet evergreen forest.

STATION 4. Punto Oeste, among grasses over sandy soil on low coastal plain.
STATION 5. Coastal plain near landing field. Snails collected on grasses and

shrubs over sandy soil.
STATION 6. Uvero. Snails collected on grasses and shrubs over sand-gravel

soils in a submesic thorn forest.
STATION 7. Talus slope l km E of Uvero in a submesic thorn forest.
STATION 8. Limestone cliffs east of Uvero aIong road-cut. Area covered with

a dense submesic thorn forest.
STATION 9. Playa Pajaro. A submesic forest with dense thickets of

Manchanilla. Cliffs with clusters of smalI bromeliads and cactae. Snails were collected
from debris and loose soil at the base of cliff.



72 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

ATLANT 1 C OCEAN

13

EL CORRAL ,9.

SARDINERA --1 BAJURA DE LOS CEREZOS

12-e LIRIO
LIGHTHOUSE I

PUNTA 0-3 t 10--5.OESTE .4~4
(ARENAS)

I 1.. 4 4 *-8
UVERO

0 ~00 K At

CAR BBEAN SEA
67.'35

FIGURE 1.- Map of Mona Island showing major physical features, atic| st.ilit,lis limi
which specimens were collected.



THOMPSON: MONA ISLAND LAND SNAILS 73

STATION 10. Lirio Lighthouse. Snails collected at night on shrubs and small
trees insubmesic f6rest.

STATION 11. Coral de Los Indios, 1.3 km NE of Lirio Lighthouse. A high mesic
forest.

STATION 12. Bajura de Los Cerezos. A limestone depression with a clarSoil

substrate in a high mesic forest.
STATION 13. Cabo Norte. An area of low sparse xeric scrub on rugged dog-

toothed limestone.
Specimens were also collected along transects from Station 8 to Station 10 and

from Station 10 to Station 12.

ACKNOWLEDGEMENTS

Financial support for field work on Mona Island was provided by the U.S. Fish
and Wildlife Service contracts No. 14-16-0008-785 and No. 85910-0339. Field work in
Puerto Rico essential to this project was sponsored by the Florida State Museum. The U.S.
Coast Guard Service at Aguadilla, Puerto Rico, through arrangements made by the U.S.
Fish and Wildlife Service, provided helicopter transportation to Mona and Monita islands.
The following persons assisted me in field work on Mona Island: Howard W. Campbell,
Steven P. Christman, Ronald I. Crombie, and Thomas A. Wiewandt. George M. Davis
(Academy of Natural Sciences, Philadelphia), Joseph Rosewater (National Museum of
Natural History), and Roth D. Turner (Museum of Comparative Zoology) loaned me
specimens in their charges and handled other queries relating to this study. The
illustrations of the island map (Fig. 1), and of Microceramus (Figs. 32-36) were skillfully
executed by Nancy Halliday, Gainesville, Florida. Wendy Zomlefer, Florida State Museum,
Staff Artist, rendered the excellent illustrations of Hoieda. Kurt Auffenberg, Florida State
Museum Biologist, produced the SEM photographs used in this paper and did many other
tasks essential for the completion of the project. I am deeply grateful to all of the above
persons for their help.

THE MOLLUSCAN FAUNA

The land snajl fauna of Mona Island was first reported upon by
Clench (1950), based upon collections made by Harry Beatty and given to
the Museum of Comparative Zoology (Harvard University), and upon
collections made by Paul Bartsch and deposited in the National Museum of
Natural History (Washington, D.C.). Clench recorded 15 species and
subspecies from the island. These are listed below along with the taxa
found during the present survey.



74 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

Clench (1950) This report

Lucidella umbonata (Shuttl.) = Helicina umbonata pitheca Thompson
Stoastomops Duertoricensis Baker = Stoastomops grada new species
Chondropoma turnerae Clench = Licina aguadillensis turnerae (CIench)

- Gastrocopta rupicola marginalba
(Pfeiffer)

- Gastrocopta pellucida (Pfeiffer)
Cerion monaensis Clench Cerion monaensis Clench
Guppya gundiachi (Pfeiffer) Suppya gundlachi (Pfeiffer)
Habroconus sp. absent

Cecilioides aperta (Swainson)
- Obeliscus sp.
- Obeliscus swiftianus (Pfeif[er)
- Subulina octona (Brug.)

Lamellaxis micra (Orbigney) Lamellaxis micra (Orbigney)
- Opeas pumilum (PfeiffeO
- Varicella nesiotes new species

Bulimulus g. guadelupensis (Brug.) absent
Bulimulus 4 ewiesi (Drouet) absent

Bulimulus d. diaphanus (Pfeiffer)
Drymaeus elonvatus beattvi Clench = Drymaeus virgulatus beattyi Clench
Brachypodella beattyi CIench Brachypodella beatt¥i Clench
Microceramus guanicanus Baker = Microceramus stenegrus new species
Holeda inaguensis (Weinland) Hoieda inaguensis (Weinland)

- Hoieda insularis eurytrema new
subspecies

- Thysanophora plagioptycha (Shuttl.)
Hemitrochus gallogovonis (Pfeiffer) Hemitrochus Rallopovonis (Pfeiffer)
Plagioptycha eucIasta (ShuttI.) = Plafioptvcha musicola fortisculpta new

subspecies

The biogeographic affinities of the Mona Island land snail fauna
are summarized in Table 1. The nine species considered to be introduced
onto the island by humans are mainly small forms, widely distributed in the
West Indies and elsewhere, and characteristically are associated with
tropical fructiculture. Three other species, Habroconus sp., Obeliscus
swiftianus, and Bulimulus d. diaphanus, also may be human-introduced but
are more restricted in their present distribution around Puerto Rico and the
Virgin Islands. The remaining 12 species are considered to be natural



THOMPSON: MONA ISLAND LAND SNAILS 75

Table 1. Biogeographicrelationships of the land snail fauna of Mona Island.

Puerto Widespread
Species Endemic Rico Hispaniola Introduced

Helicina umbonata pitheca + +
Stoastomops grada +
Licina aguadillensis tumerae +
Gastrocopta rupicola marginalba +
Gastrocopta pellucida +
Ccrion monaensis + +
Guppya gundlachi
Habroconits *. +
Cecitiodes aperta +
Obeliscus sp. +

Obeliscus.swiftianus +
Subulina octona +
Lamellaxis micra +

Opens pumilum +

Varicella neslotes + +
Bulimulus d. diaphanus + 1
Drymacus virgulatus beattyi + +
Brachypodelid beattyi + +
Microcemmus stenegrus + +
Hojeda inaguensis +
Hojcda insularis eurytrema +
Thysanophora plagioptycha

+

Hemitrochus kallopovonis
Plagioptycha musicola

fortisculpta + +



76 BULL. FLORIDA SrATE MUS., BIOL. SCI. 31(2)

inhabitants of the island. Of these, Six are endemic species, and three are
endemic subspecies, yielding an endemism of 50% at the species level and
83% at the subspecific level for the native land snail fauna of the island. Of
the endemic taxa, four have systematic affinities to species occurring on
Puerto Rico, three are related to Hispaniolan species, and two are of
uncertain relationships.

HELICINIDAE

Helicina umbonata pitheca THOMPSON

Lucidella umbonata (Shuttleworth), Clench 1950 :271 ; fig. 2.
Helicina umbonata pitheca Thompson 1982: 15- 17 ; Figs. 36-43.

The taxonomic status of the Mona Island population of Helicina
umbonam has been discussed recently (Thompson 1982). H. u. pitheca is
distributed ubiquitously on the island. Live specimens commonly are found
aestivating on low shrubs, grasses, and vines. The brightly colored shell is
adaptive for a cryptic existence in this habitat.

Stoastomops grada new species

Stoastomopspue,Yoticensis Baker, Clench 1950:271.
SHELL (Figs. 2-5).-- Small 2.2-2.6 mm wide; 0.81-0.92 times as high

as wide; depressed turbinate-conical with 3.9-4.2 whorls. Two color phases:
one phase citron yellow, other phase light orange (holotype). Whorls
subangular at the periphery and scalariform; flattened or weakly concave
above periphery, convex below, umbilical region nearly flat. Protoconch
(Fig. 10) raised, slipper-shaped, consisting of 3/4 of a turn; 0.37 mm long
and 0.26 mm wide; sculptured with a few weak incremental striations and
irregular, oblique spiral striations. Subsequent half whorl with about 10
fine, raised spiral threads, which continue onto lower whorls where they
become enlarged and are crossed at irregular intervals by oblique varix-like
fimbriations (Fig. 11); 7-10 spiral threads on dorsal surface of last whorl.
Spiral threads below periphery weak, discontinuous, and poorly defined on
base (Fig. 12). Aperture ovate-auriculate in shape; 0.44-0.53 times height of
shelli 0.71-0.80 times as high as wide. Columellar lip conical in



THOMPSON: MONA ISLAND LAND SNAILS 77

.i~-'.-#.A#A

7~

Bil<M./AEJVN~
---.'..#..£-%%£illwi.l/kld

~'

4

9

FIGURES 2-9. - FIG. 2-5: Stoastomops grada new species, Paratypes (UF 40715) (X
24). FIGS. 6-9: Stoastomops puertoricensis Baker (UF 40714; 7.0 km SE Guanica, Puerto
Rico) (X 24).



78 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

shape, hollow internally (Figs. 13-15). Outer periphery of columellar lip
angular so that it appears, falsely, to be rimate.

Measurements in mm based on 29 specimens are given below.

n height width aper. h. aper. w. whorls
UF 40678 15 1.9-2.1 2.2-2.6 0.93-1.05 1.24-1.43 4.0-4.2
UF 24989 3 1.9-2.1 2.2-2.4 0.93-0.99 1.19-1.36 4.0-4.2
UF 40677 10 1.9-2.1 2.1-2.4 0.87-0.99 1.24-1.36 4.0-4.1
Holotype 1 1.98 2.17 0.93 1.30 4.1

Specimens from the bluffs near Sardinero generally are larger than
specimens from other localities. This may reflect the more favorable mesic
habitat characterizing that area. Sexual dimorphism in size cannot be
determined from the material on hand, because I found only dead shells on
the two occasions I visited the island.

OPERCuLUM (Figs. 16-18).-- Narrower than in S. pue,Yoncensis
Baker (Figs. 19-21). Calcareous plate weakly granular with a low, narrow,
weakly arched ridge closely paralleling the columellar margin (Figs. 17,18).

TYPE LOCALITY.-- Mona Island, Coral de Los Indios, 1.3 km
northwest of the Lirio lighthouse. HOLOTYPE: UF 40676; collected 22
May 1974 by Fred G. Thompson from leaf litter along the base of a low
ledge in a mesic forest. PARATYPES: UF 40677 (49); UF 40719 (SEM
opercula); same data as holotype. Other paratypes from Station 1 (UP
24989,9 specimens), Station 3 (UF 40678,30 specimens; UF 40715, 4 SEM
shells), Station 8 (UF 40679,30 specimens), and Station 9 (UF 40680, 9
specimens). All were found along limestone ledges in leaf litter. Isabella
Anchorage (USNM 430974, 13 specimens).

DISTRIBUTION.-- Endemic to Mona Island.
REMARKS.-- This species is most similar in shape to S. adamsi

Baker from Jamaica. It differs from S. adamsi by its sculpture. S. adamsi
has 6-7 spiral threads above, and 28-29 below on the last whorl (Baker
1934:10; 1935, fig. 1). The threads are weaker than in S. gmda and uniforrn
in size over the surface of the whorl. S. grada is similar to S. puertoricensis
Baker in sculpture, but differs in shape and opercular structure. In S.
pumo,icensis the spire is concave-conical with the whorls separated by a
deeply incised suture (Figs. 6-9). The dorsal surface of the whorls usually
has a shallow furrow below the suture (Fig. 8). The operculum is broader
and the calcareous plate bears a thick, wide, straight vertical ridge that is
offset from the columellar margin (Figs. 19-21).



THOMPSON: MONA ISLAND LAND SNAILS 79

13

141 15

FIGURES 10-15.- Stoastomops grada new species, Paratypes. FIGS. 10-11: UF 40715
(X 80). FIG. 12: UF 40715 (X 53). FIG. 13: UF 40718 (X 27). FIG. 14: UF 40717 (X 27).
FIG. 15: UF 40717 (X 16).



80 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

16 19

17 20

18 21
FIGURES 16-21. FIGS. 16-18: Stoastomops grada new species, opercula (UF 40719).
FIGS. 19-21: Stoastomops puertoricensis Baker, opercula (UF 40713, 7 km SE Guanica,
Puerto Rico). (X 53).



THOMPSON: MONA ISLAND LAND SNAILS 81

Baker ( 1941 : 1 ) stated that the columella of S. puertoricensis
sometimes is rimate (narrowly perforate). This is incorrect. The outer edge
of the columellar lip is angular so that when viewed from the front it
appears to form a rimate opening into the columella. Such a condition does
not exist in the Helicinidae, because the parietal shelf partially forms a short
tube that extends into the columellar lip as a blind caecum (Figs. 13-15). A
perforation would puncture this tube.

Baker (1934:10), on Pilsbry's advice, described S. adamsi as a new
species, although Baker considered it to be synonymous with Helicina tenuis
Adams, September 1849, p. 14. Pilsbry contended that Helicina tenuis
Adams is not an available name, because it is preoccupied by Helicina tenuis
Pfeiffer, April 1949, p. 124, not withstanding the fact that Adams (1849:16),
two pages later, placed tenuis Adams in Trochatella. Baker ( 1935 : 63)
surreptitiously reverted to the use of Adams name as Stoastomops tenuis
(Adams). The Jamaican species should be referred to as Stoastomops
adamsi Baker.

ETYMOLOGY.-- The name grada is from the Latin gradus, a step or
stairs, and refers to the scalariform step-like whorls.

ANNULARIIDAE

Licina aguadillensis tumerae (CLENCH)

Chondropoma tumeme Clench 1950:271-272, fig. .
Licina (Choanopomops) aguadillensis tumerae Baker 1962a: 23 .

This snail is nearly ubiquitous on Mona Island. It was collected at
all stations except 2 and 5, which are on loose sand. Baker (1962a) referred
populations from Cerro Capron, near Guanica, Puerto Rico, to this
subspecies and places all the Puerto Rican Annulariinae in Choanopomops
Baker 1928. The operculum of tumerae (Figs. 22, 23) is typical of the
subgenus by having on the outer surface a partial carcareous [amelia that is
reinforced from beneath by calcareous ribs and deposits. The face of the
underlying chitinous plate is covered with calcareous granules



82 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

3$* .

23 24

22

26

FIGURES 22-26. FIGS. 22-23: Licina aguadillensis turnerae (Clench),opercula (UF
40720). (X 18). FIGS. 24-26: Varicella (Sigmataxis) nesiotes new species, Paratype (UF

40833). FIG 24 (X 11). FIG. 25: Sculpture of body whorl at inset in Fig. 24. (X 212). FIG.

26: Sculpture ofcolumella(X 108)



THOMPSON: MONA ISLAND LAND SNAILS 83

PUPILLIDAE

Gastrocopta mpicola marginalba (PEEWFER)

Collected in leaf litter samples from Stations 1 and 3.

Gastocopta pellucida (PFEIFFER)

Collected in leaf litter from Stations 3, 8, 9, and 11.

CERIONIDAE

Cerion monaensis CLENCH

Abundant and generally distributed on the coastal plains along the
south side of Mona Island. Locally distributed on the limestone plateau.

HELICARIONIDAE

Guppya gundlachi (PFEIFFER)

Dead shells were collected in leaf litter at Stations 3, 11, and 12 in
patches of mesic forest. Live snails were found crawling on dead leaves at
Station 3.

Habroconus sp.

Clench (1950:273) recorded two specimens of an apparently
undescribed species which were collected at Isabella Anchorage
(Sardinero). Apparently these are the same as the species common on
Puerto Rico. Habroconus was not found on the island during this survey.
The specimens reported by Clench cannot be located in the Musuem of
Comparative Zoology or the National Museum of Natural History.
Apparently they are lost.

FERUSSACIIDAE

Cecilioides aperta (SWAINSON)

Collected at Stations 1 and 3; sifted from loose humus-rich soil.



84 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

SUBULINIDAE

Obeliscus swiftianus (PEEIFFER)

Dead shells were recovered from leaf litter at Stations 1,3,8,9, and
12. The species appears to be restricted to mesic forests along the
escarpment on the south side of the island and in a mesic forest at Station
12.

Obeliscus sp.

A single specimen of an unidentified species was collected at
Station 12. It is similar to 0. simpsoni Pilsbry from Hispaniola but is
immature, and specific identificaton is uncertain.

Subulina octona (BRUGUIERE)

Nearly ubiquitous in terrestrial habitats on the isladd.

Lamellaxis micra (ORBIGNEY)

Collected in leaf litter at Station 1, 3, and 12 in mesk forest.

Opeaspumilum (PFEIFFER)

Found in leaf litter at Station 3.

OLEACINIDAE

Varicella (Sigmataxis) nesiotes new species

SHELL (Figs. 24,27-29).-- Very thin, elongate-turrete. Adults
about 0.31-0.34 times as wide as high and proportionally more slender than
juveniles  Spire about 0.60-0.64 times length of shell (0.61 in holotype),
nearly straight-sided in outline. Shell uniformly colored; translucent; axis
twisted internally. Whorls 5.3-5.5 in large specimens (5.0 in holotype);
embryonic shell with 1.8 whorls. Suture deeply impressed and weakly
crenulated by the striate sculpture. Whorls of spire moderately



THOMPSON: MONA ISLAND LAND SNAILS 85

K

/.1.\
/ 1

28 29
27 0 1 2

mm

FIGURES 27-29.- Varicella (Sigmataxis) nesiotes new species. FIG. 27: Paratype (UF
40832). FIGS. 28,29: Holotype (UF 40831).



86 BULL. FLORIDA STATE MUS., BIOL SCI. 31(2)

arched, very narrowly shouldered along suture. Body whorl in large
specimens may be fiattened or even weakly concave peripherally. Periphery
of last whorl slightly below middle of whorl. Embryonic whorls glossy and
smooth. Subsequent whorls sculptured with nearly equally spaced arcuate
transverse striations that are continuous across surface of whorl, about 8-10
striations/mm on last whorl. Striations U-shaped and about as wide as deep
(Fig. 25), diminishing slightly near base. Interspaces between striations flat
and glossy. Aperture elongate-pyriform, about half as wide as high and
about 0.36-0.40 times length of shell (0.39 in holotype). Columella weakly
concave in outline; generally slightly twisted at base but may be evenly
arched in large specimens (Fig. 29). Parietal wall with a thin hyaline deposit
that is slightly thickened and granular over columella (Fig. 26).

Measurements in mm of seven paratypes and the holotype (in
parenthesis) are as follows: length 4.7-5.9 (4.68), width 1.6-1.8 (1.68),
aperture height 1.89-2.10 (1.82), and aperture width 1.0 (0.98).

TYPE LOCALITY.-- Mona Island, Sardinero (Station 3). Specimens
were collected along the base of a limestone bluff in leaf debris.
HOLOTYPE: UF 40831; collected 21 May 1974 by Fred G. Thompson.
Paratypes: UF 40832 (10), UF 40833 (SEM shell); same data as the
holotype.

DISTRIBUTION:- Endemic to Mona Island. Other localities from
which it was collected are Stations 1, 8, and 12.

REMARKS.-- Varicella nesiotes is closely related to two species from
Hispaniola, K verberata (Pilsbry) and K una (Pilsbry). Both were described
as species of Sigmataxis, which then was regarded as a subgenus of Spiraxis
(Pilsbry 1907:43-44). Neither has been mentioned in the literature since it
was named. These three snails form a disparate group from other
Sigmataxis by having a tendency for the columella to be truncate and by
having a relatively enlarged body whorl . Other Sigmataxis, all of which are
Jamaican, have a strongly twisted columella and a proportionally smaller
body whorl . In these respects the Hispaniolan species and K nesiotes are
intermediate between Sigmataxis and Varicella (s. gen. Variccllula), which is
also Jamaican. Their subgeneric relationships cannot be clarified until
anatomical material is examined.

K verbemta is a more robust species than K nesiotes and has a
proportionally larger, more inflated body whorl . In addition K verberata
has a more conspicuously twisted columella, and the striations are nearly
obsolete below the periphery of the last whort. K una is a smaller species
than K nesiotes, being just over 4 mm long. Its striations are closer
(12/mm), and the columella is strongly twisted near the middle as opposed
to near the base as in K nesiotes.

EIYMOLOGY.-- The specific name nesiotes is from the classical
Greek meaning insular.



THOMPSON: MONA ISLAND LAND SNAILS 87

BULIMULIDAE

Bulimulus guadalupensis (BRUGUIERE)

This species was recorded from Mona Island by Clench (1950:273)
as B. g guadalupensis and as B. g. eyreisii (Drouet). Breure (1974:15-26, 46-
47) showed that eynesii is a distinct species, and that the specimens
recorded from Mona Island are typical guadalupensis. I did not encounter
guadalupensis on Mona, even though I collected at the same stations from
where Clench recorded it. Apparently it is no longer extant on the island.
Breure (1974:51) suggested that the occurrence of this species outside of
the Windward Islands is attributable to human introductions.

Bulimulus d. diaphanus (PFEIFFER)

Found at Stations 1, 4, 5, 8, 11, and 12. It was most abundant on
the south coastal plain among clumps of grasses. It is generally present on
the plateau but is sparser in its occurrence there. Breure (1974:32)
recorded this species from Mona Island based upon specimens in the MCZ.

Domaeus vimulatus beato,i CLENCH

Dgmeaus elongams beato/i Clench, 1950:273-274, figs. 4-6.
D. virgulatus (Ferussac) (=elongatus Bolten) is widespread on

Puerto Rico and its satellite islands, the Virgin Islands, St. Martin, St.
Eustatius, Curacao, Bonaire, and Amba. Baker (1924:80-85) presented
evidence suggesting that the species was introduced through commerce to
the last five islands. Its wide distribution on Puerto Rico and the Virgin
Islands apparently is natural (Pilsbry, 1899:23-27). Domaeus vimulatus is
highly variable in color and, to a lesser extent, in relative obesity. Several
names have been proposed for some of these variants, including h7iaceus
Ferrusac (see Baker, 1962:120). D. v. beatty: is most similar in shape and
size to the fossil form crtinctus (Pfeiffer) from St. Croix. It is least similar to
the larger, more obese forms occurring on Puerto Rico. It is distinguished
from all forms of vitgulatus by having a narrow, elongate aperture that bears
a reflected basal lip. D. v. beato,i is common and nearly ubiquitous on Mona
Island. It Was collected at all stations. There is considerable local variation
in size and obesity, and Mona populations overlap in these traits with
extinctus. Measurements of selected specimens of beattyi taken from four
lots to show maximum variation are given in Table 2.



88 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

Table 2. Measurements in mm of selected specimens of Drymaeus v. beattyi taken from four
population samples to show maximum variation in size and proportions.

Station: 4 6 10 12

N 44 41 21 6
Length 19.5-24.0 19.1-26.2 21.6-27.4 19.2-22.4
Width 8.3- 9.7 8.2-10.5 9.0-11.3 8.3- 9.2
Aperture H. 9.1-11.4 9.2-11.9 10.3-13.1 9.3-10.4
Aperture W. 5.1- 6.0 5.1- 6.4 5.3- 6.8 5.1- 5.7
Whorls 5.6- 6.3 5.6- 6.5 5.7- 6.8 5.8- 6.2
Width/Length 0.38-0.46 0.38-0.46 0.38-0.48 0.40-0.44
Ap. W/Ap. H 0.52-0.62 0.50-0.60 0.48-0.56 0.52-0.55
Ap. H/Length 0.42-0.51 0.43-0.53 0.43-0.51 0.46-0.51



THOMPSON: MONA ISLAND LAND SNAILS 89

UROCOPTIDAE

Brachypodella beattyi GENCH

Brachypodella beattyi Clench 1950:275; fig. 3.
B. beattyi is generally distributed on Mona Island. It was found at

Stations 1, 3, 4, 11, and 12. This species was described as closely related to
B. pallida (Pfeiffer), a species found on Puerto Rico and the Virgin Islands
of St. Thomas, St. Johns, and Tortola (Pilsbry 1904:84-85). B. beattyi differs
from B. paUida in several respects, including thin solid ribs and finer,
sparser costulate sculpture on the embryonic whorls (Fig. 30). B. pallida has
thick hollow ribs and the sculpture on the embryonic whorl consists of
denser, heavier axial threads (Fig. 31). In these respects B. beattyi is nnore
similar to some forms of the B. dominicensis complex from Hispaniola than
it is to B. pallida.

Microcemmus stenegrus new species

Microcemmus guanicanus Baker, Clench 1950:275.
SHELL (Figs. 32,34,35).-- Elongate-conical, about 0.40-0.48 times

as wide as hjgh. Spire slender, straight-sided, regularly increasing in
diameter to base. Imperforate. Color opaque white with sparse vertical
wavy brown bars that are broader and closer on upper whorls but are clearly
defined throughout length of spire. Axis solid with a very weakly twisted
callus. Whorls 8.3-10.5 in specimens with expanded peristome; 2.0
embryonic whorls. Suture deeply impressed. Whorls angular at periphery,
particularly on upper spire. Body whorl with weak basal-lateral spiral ridge.
First half embryonic whorl smooth. Subsequent embryonic whorls
sculptured with uniform, thin, regularly spaced, vertical thread-riblets.
Postembryonic whorl sculptured with heavier oblique ribs that are slightly
recurved near the upper ends and frequently broken and irregular in
thickness, more so on lower whorls than upper. Ribs slightly thickened at
base, not crenulating suture. About 42-55 ribs on penultimate



90 BULL. FLORIDA SrATE.MUS., BIOL. SCI. 31(2)

30 31
a 8

1mm

32 , , 33
1mm

FIGURES 30-33.- Fig. 30: Brachypodella beattvi Clench, (UF 40870); sculpture of
apical whorls. FIG. 31: Brachypodella Dallida (Pfeiffer), (UF 40878), sculpture of apical

whorls. FIG. 32: Microceramus steneerus new species. Paratype (UF 40830). FIG. 33:
Microceramus guanicanus Baker, (UF 40876, 10 km SE Guanica, Puerto Rico).



THOMPSON: MONA ISLAND LAND SNAILS 91

whorl in larger specimens (55 in holotype). Ribs continuous, but
diminished on base of last whorl. Aperture sub-rhomboid; slightly wider
than hi~h, about 0.20-0.27 times height of shell; lying at an angle of about
400-48 to shell axis (430 in holotype). Peristome nearly uniformly
expanded and moderately thickened, incomplete across parietal wall.
Columella slightly oblique to shell axis.

Measurements in mm of holotype: length 6.85, width 2.80, apepre
height 1.54, whorls 10.1. Measurements of specimens from four population
samples selected to show population variation are given in Table 3.

TYPE LOCALITY.-Mona Island, Sardinero; at base of limestone cliff
in mesic forest (Station 1). HOLOTYPE: UF 40828; collected 12
November 1978 by Fred G. Thompson. PARATYPES: UF 40829(18),
same locality as holotype; UF 40830(91), Station 3.

DISTRIBUTION.-- This snail is generally distributed over the island
in mesic and submesic microhabitats. It was collected at Stations 1,4,8,9,
11, 12, and 13.

REMARKS.-- Microceramus stenegnts is a member of a small group
of southern Caribbean species that also includes M bonairensis (Smith) and
M. guanicanus Baker by virture of having ribs that do not crenulate the
suture and by being imperforate. M. bonairensis is confined to the Dutch
Leeward Islands and includes three subspecies that differ principally in size
(Baker 1924:95-98). M. guanicanus is known only from a small xeric
limestone peninsula east of Guanica, Puerto Rico. M. stenegrus is most
similar to M. guanicanus in size and sculpture. It differs from M. guanicanus
by having a slender, attenuate spire that is uniformly conical in large
specimens, whorls that are angular at the periphery, a more deeply
impressed suture, generally a weak baso-lateral ridge on the last whorl, ribs
that are much heavier and closer, and a more sharply defined color pattern
throughout the length of the shell . M. guanicanus (Figs. 33 , 36, see also van
der Schalie, 1948: pl. 7, fig. 4) has a relatively obese spire that becomes
turrete in larger specimens, the whorls are rounded with a shallow suture,
the last whorl lacks a baso-lateral ridge, the ribs are narrower, lower, and
more widely spaced, and the color pattern is distinct only on the upper
spire. M. stenegms is a more slender species than M. guanicanus. Both
species show considerable variations in the size of the body whorl and the
reflection of the peristome. Measurements of major diameter and total
length incorporate both of these variables, and on the basis of overall size
the two species overlap (Table 3). Measurements of the minor diameter



92 BULL. FLORIDA SrATE MUS., BIOL SCI. 31(2)

Table 3. Measurements in mm of specimens from samples of Microcemmus selected to show
variations in size.

M. stenegrus n. sp. M. guanicanus Baker

Station: 3 11 12 13 UF 40876 UF 40877

N 35 14 10 9 28 17
Major D. 2.0-2.5 2.0-2.4 2.3-2.7 2.3-2.6 2.5- 3.1 2.7- 3.0
Length 4.3-6.4 4.3-5.4 5.0-6.1 5.6-6.4 5.1- 7.3 5.7- 7.2
Maj. D./Length 0.38-0.47 0.41-0.51 0.39-0.48 0.39-0.44 0.40-0.51 0.39-0.47
Whorls 8.3-9.8 7.9-8.9 8.4-9.2 9.0-9.5 8.3-10.0 8.8-10.3
Aper. H 1.1-1.5 1.1-1.3 1.3-1.5 1.2-1.6 1.3- 2.0 1.4- 2.2
Aper.H./Length 0.21-0.27 0.23-0.28 0.22-0.26 0.21-0.27 0.23-0.29 0.23-0.27
Minor D. 1.8-2.2 1.8-2.1 2.1-2.4 2.1-23 2.2- 2.8 2.2- 3.0
Spire 3.3-5.0 2.7-4.3 3.7-5.9 4.4-5.1 3.6- 53 3.6- 6.1
Min. D./Spire 0.44-0.55 0.50-0.64 0.39-0.60 0.42-0.49 0.50-0.65 0.49-0.67



THOMPSON: MONA ISLAND LAND SNAILS 93

..,5,6, 5.  ,
hkal :

74~
4-# 4 C ' · i*.I «*"~442_Ir-/

34 ' 35 36
' 1

3mm

FIGURES 34-36.- FIGS. 34-35: Microceramus stenegrus new species (Fig. 34, Holotype
[UF 40828]; Fig. 35, Paratype [UF 40830]). FIG. 36: Microceramus Ruanicanus Baker (UF
40876).



94 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

and the length of the spire include less variable parameters, and significant
differences between the two species occur in the minor diameter and its
ratio to the length of the spire. Most M. stenegrus have a minor diameter of
1.8-2.2 mm and a minor diameter/spire ratio of 0.39-0.52 mm, whereas most
M. guanicanus have a minor diameter of 2.3 -3 .0 mm and a minor
diameter/spire ratio of 0.52-0.67 mm. These two differences apply to about
90% of the specimens examined.

Specimens of M. guanicanus examined for comparison. PUERTO
RICO: 7 km SE Guanica (UF 40877, 27 specimens); 10 km SE Guanica
(UF 40876,38 specimens).

ETYMOLOGY.-- stenegms, from the Classical Greek stenegros
meaning narrow, tight, alludes to the slender, compactly coiled spire.

SAGDIDAE

Hojeda inaguensis (WEINLAND)
(Figures 37-42)

Collected at Stations 1, 3, 8, 9, 11, 12, and 13 in leaf litter. This
snail is widely distributed on the Florida Keys, the Bahama Islands,
Hispaniola, and Mona Island. The use of the name inaguensis by Clench
(1950:272) for the Mona Island and Hispaniolan populations is supported
by anatomical data. I dissected preserved specimens from Station 12 (UF
40839). The reproductive anatomy essentially is identical to that of
specimens from Stock Island, Florida, described by Baker (1940:60).

Pilsbry (1940:984, Figs. 571) illustrates a specimen from Boca Chica
Key, Florida, as typical for the species. The specimen has an umbilical
opening that is about 1/4 (0.25) the width of the shell. I have examined
many series of specimens from throughout the range of the species, and
none approaches this condition. The umbilicus generally is much narrower,
being about 0.15-0.19 times the width of the shell. The snail is conservative
in its geographic variation, and the illustrations given in this paper (Figs. 37-
42) are representative for the species throughout its range. The sculpture
and protoconch characteristics are illustrated in Figures 43-45.

Measurements in mm of five specimens from Station 11 on Mona
Island are given for comparisons with the following species.



THOMPSON: MONA ISLAND LAND SNAILS 95

i -'' ,
f P

40

j -74. /*Rk\,\St>
I ..'Cl

\,5 \ea/t--
38 41 ~--»*

i
 -
 

I 
*
,
1
3
=
«
1
/
5

\Cit#Pe'q",6,
39

, i i ,
3mm 3mm

FIGURES 37-42.- Hoieda inaguensis (WeinIand) (UF ). FIGS. 37-39: (UF 40844).
FIGS. 40-42: (UF 41575).



96 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

height width apert.h. apert.w. umbil.w. whorls
2.05 3.16 1.24 1.43 0.50 3.9
2.02 3.29 1.30 1.55 0.50 4.0
2.17 3.39 1.24 1.49 0.62 4.0
2.42 3.53 1.30 1.67 0.62 4.2
2.54 3.60 1.24 1.74 0.62 4.2

Hojeda insularis insularis new species

Hojeda inaguensis (Weinland ) Thompson 1976 ; 152.
SHELL (Figs. 55-57).-- Small, about 3.4-3.7 mm wide. Depressed-

turbiniform, 0.57-0.64 times as high as wide. Spire low and broadly conical,
not depressed, dome-shaped as in H. inaguensis (Fig. 55). Umbilicus
moderately wide, about 0.23-0.28 times width of shell. Shell relatively thick
compared to other Hojeda, opaque, milky-white . Whorls about 4. 0-4. 1 in
mature specimens. Suture deeply impressed. Protoconch (Figs. 49-51)
about 1.4-1.5 whorls with numerous very fine spiral threads below periphery
as in H. inaguensis (Figs. 43-45); last 1/4 whorl of protoconch with fine
radial growth striations. Following whorls rounded; relatively narrow
compared to H. inagtiensis (Figs. 37-40); sculptured with numerous
incremental growth striations that are irregular in intensity, becoming
slightly rough near peristome. Sculpture more rugose than in H. inaguensis
(Fig. 43) and nearly uniform over surface of whorls. Aperture semi-lunar in
shape, 0.75-0.88 times as wide as high, height  0.57-0.67 times height of shell,
width 0.44-0.47 times width of shell. Peristome slightly thickened with an
internal callus and blunt-edged at mamrity. Columellar lip weakly ref[ected.
Parietal callus conspicuously thickened at maturity (Fig. 55) in contrast to
other species of Hoje(la.

Measurements in mm converted from micrometer units of five
specimens selected to show variation are as follows:



THOMPSON: MONA ISLAND LAND SNAILS 97

43 1lllilglimu,EA-40~ -

FIGURES 43-48.- FIGS. 43-45: Hoieda inaguensis (Weinland); UF 40777. Fig. 43, X
15; Fig. 44, X 50; Fig. 45, X 150. FIGS. 46-48: Lacteoluna selenina (Gould); UF 40820
(Stock Island, Monroe Co., Florida). Fig. 46, X 15; Fig.47, X 30; Fig.48, X 150.



98 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

49 52

4

FIGURES 49-54.- FIGS. 49-51: Hoieda i. insularis new species, Paratype (UF 40779).

Fig. 49, X 20; Fig. 50, X 53; Fig. 51, X 159. FIGS. 52-54: Hoieda insularis eurytrema new

subspecies, Paratype (UF 40778). Fig. 52, X 20, Fig. 53, X 53; Fig. 54, X 159.



THOMPSON: MONA ISLAND LAND SNAILS 99

height width apert.h. apert.w. umbil.w. whorls
Holotype 2.29 3.60 1.30 1.67 0.87 4.1
Paratype 2.05 3.41 1.18 1.59 0.87 4.0
Paratype 2.05 3.60 1.30 1.61 0.93 4.0
Paratype 2.17 3.53 1.24 1.55 0.93 4.0
Paratype 2.23 3.72 1.30 1.74 0.99 4.1

TYPE LOCALITY:-Monito Island (1809'30"N, 67057'15"W).
HOLOTYPE: UF 40814; collected 20 May 1974 by Fred G. Thompson.
PARATYPES: UF 40815 (76), UF 40779 (1 SEM shell), UF 40821 (2
SEM shells); same data as holotype.

REMARKS.-- Hojeda includes four other species: H. inaguensis
(Weinland) is widely distributed from the Florida Keys, through the
Bahama Islands, Hispaniola, and Mona Island ; H. vanattai Baker ( 1924) is
endemic to Aruba; H. boothiana (Pfeiffer) is a large species (5 mm wide)
that occurs in Cuba; H micromph(ila Pilsbry is widely distributed on
Hispaniola. H. insulads differs from all by the same characteristics in which
it differs from H. inaguensis.

In general appearance , the shell of H. i. insularis suggests a
relationship to Lacteoluna, which also has spiral sculpture on the
protoconch (Figs . 46-48). However, the spiral sculpture in Lacteoluna is
coarser, and it occurs over the entire surface of the protoconch. In Hojcda
it is confined to the perjphery. Moreover, all the species placed in
Lacteoluna (s .s .) by Baker ( 1935a :52) have discoidal shells with a bluntly
angular periphery.

The discoidal form of the following subspecies approaches that of
Lacteoluna. The generic relationships of these two new taxa remain
tentative until their reproductive anatomies are examined; nevertheless,
their protoconch sculpture strongly indicates congeneric relationships with
Hojeda.

Hojeda insularis eutytrema new subspecies

SHELL (Figs. 58-60).-- Similar to H. i. insularis iii most aspects of
color, sculpture, and protoconch characteristics (Figs. 52-54). It differs by
having a thinner, transparent shell. The spire is more depressed, with the
shell being about 0.53-0.57 times as high as wide. The umbilical perforation
is relatively broader, being about 0.26-0.30 times the width of the shell. l'lie
parietal callus is very thin and is nearly indistinguishable.



100 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

0 I f f~ -*--*2~5- - h, N-1 ·· .r.f -
FS
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i

\Y I.-4+11£*lk'lillill'llilmi jy .r:f -f/=<- -L -1 _ -. ./„ ·55~

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.'.' -I~ - :ip £# I

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FIG URES 55-60.- FIGS. 55-57: Hoieda i. insularis new species, Holotype (UF 40814).
FIGS. 58-60: Hoieda insularis eurvtrema new subspecies, Holotype (UF 40816).



THOMPSON: MONA ISLAND LAND SNAILS 101

Measurements in mm converted from micrometer units based on
the five largest specimens available from the type locality follow:

height width apert. h. apert. w. umbil. w. whorls
Holotype 1.74 3.16 1.05 1.30 0.87 3.9
Paratype 1.55 2.91 0.88 1.24 0.81 3.7
Paratype 1.55 2.91 0.93 1.30 0.87 3.7
Paratype 1.61 2.98 0.99 1.24 0.87 3.8
Paratype 1.80 3.35 - 0.93 4.2

TYPE LOCALITY:- The base of Iimestone cliffs at Playa Pajaros,
Mona Island (Station 9). HOLOTYPE: UF 40816; collected 23 May 1974
by Fred G. Thompson. PARATYPES: UF 40817 (5), UF 40778 (1 SEM
shell), same data as holotype; UF 40819 (6), Coral de Los Indios (Station
11). All specimens are dead shells recovered from leaf litter.

REMARKS.-- H. i. euiytrema differs from H. i. insulans to an extent
that would constitute specific distinctions among most members of this
family. Nonetheless the two taxa are very similar in appearance and
apparently are closely related. The two samples from Mona Island consist
of only a few specimens and most of these appear to be immature.

ETYMOLOGY.-- The name eugtrema is from the Classical Greek
ewys, meaning wide, and trema, a hole, and alludes to the wide umbilical
perforation of this taxon.

POLYGYRIDAE

Thysanophom plagioptycha (SHUTTLEWORTH)

A single shell was recovered from leaf litter in a patch of mesic
forest at Station 11.

XANTHONYCHIDAE

Hemitrochus gallapavonis (PFEIFFER)

Found at Stations 2,4,5, and 6. This snail occurs in the Turks and
Caicos Islands. It has been found on Mona Island only on the south coastal
plains, the portion of the island that was homesteaded. It probably was
introduced, as discussed by Clench (1950:250).



102 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

Plagiopopcha musicola fomsculpta new subspecies

Plagioptycha euclasta (Shuttleworth), Clench 1950:276.
SHELL (Figs. 61-65).-- Depressed-helicoid with a low dome-shaped

apex. Shell 0.51-0.66 times as high as wide. Brown, opaque; aperture,
peristome, and columella lighter brown or dusky. Suture weakly impressed.
Umbilicate; perforatien half covered by columellar reflection. Whorls 4.6-
4.7 in larger specimens. Embryonic whorls 1.8. Upper whorls weakly arched
between sutures. Body whorl bluntly angulate at periphery and descending
slightly to the aperture. Peripheral angle of last whorl lying below middle of
whorl. Body whorl strongly curved below periphery, moderately arched
above. First 1.2 embryonic whorls smooth. Subsequent whorls with strong,
oblique, recurved axial ribs that are continuous across the surface of the
whorls and into the umbilicus where they are only slightly diminished in
size. Interspaces about 2-3 times as wide as ribs. Ribs smooth and glossy,
interspaces sculptured with a meshwork of extremely fine granules.
Aperture semi-elliptical, about 0.58-0.63 times as high as wide. Peristome
incomplete across parietal wall; simple, not reflected or thickened internally.
Parietal wall with a thin but well defined parietal callus. Columella nearly
vertical and widely reflected above, continuing obliquely into basal lip.

Measurements in mm of the holotype and three paratypes selected
to show maximum variation follow:

height width apert. h. apert. w. whorls
Holotype 6.1 9.8 3.7 5.6 4.7
UF 40825 5.2 10.0 3.2 5.5 4.6
UF 24979 6.8 10.3 3.8 6.3 4.7
UF 40826 6.7 11.3 3.7 6.3 4.7

TYPE LOCALITY.-- Mona Island, Bajura de Las Cerezas (Station
12). HOLOTYPE: UF 40823, collected 13 November 1978 by Fred G.
Thompson. Paratypes: UF 24979 (3), same data as holotype; UF 40825 (3),
Coral de Los Indios (Station 11); UF 40824 (1), Lirio Lighthouse (Station
10); UF 40826 (1), 1 km W Uvero (Station 7); MCZ 171028 (2), "Mona
Island." Apparently this snail is arboreal. Fresh dead shells and one live
juvenile were found in bromeliads.

REMARKS.-- P. m. fomsculpta is closely related to P, m. musicola
(Shuttleworth), from which it differs by the shape of the shell, the



THOMPSON: MONA ISLAND LAND SNAILS 103

-4.id I'llill.Ikbdi:/. 1 1\

~7/f61 62 63's.*,..--

64 65 66

67 68 69

%6.

70 71 72

FIGURES 61-72.- FIGS. 61-65: Plagioptycha musjcola fortisculpta new subspecies.
FIGS. 61-63: Holotype (UF 40823). FIG. 64: Paratype (UF 24979). FIG. 65: Paratype
(UF 40826). FIGS. 66-69: Plagioptycha musicola euclasta (Shuttleworth). FIG. 66: ANSP
28305; St. Thomas Island, Virgin Islands. FIGS. 67-69: ANSP 1032; St. Thomas Island,
Virgin Islands. FIGS. 70-72: Plagioptycha m  musicola (Shuttleworth). ANSP 256407;
Cabo Rojo, Mayaguez Dist., Puerto Rico. All figures X 5.5.



104 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

shape of the aperture, by having more whorls. and by having a shallower
suture . P. m . fortisculpta (Figs. 61 , 64, 65 ) has a depressed dome-shaped
spire, and the peripheral angle lies below the middle of the last whorl. The
apertitre is narrowly elliptical. In mature specimens the shell consists of
about 4.6-4.7 whorls that are separated by a shallow suture, which results in
relatively flattened whorls between the suture. P. m. musicola (Fig. 70) has
a helicoid or depressed helicoid spire and the periphery of the last whorl lies
at or above the middle of the whorl. The aperture is more broadly elliptic.
Seldom does the shell have more than 4.2 whorls. with a maximum of 4.4
whorls (33 lots examined; ANSP, UF), and the suture is deeply impressed.
producing strongly arched whorls between the sutures. P. m . f01'tiSCIllptll

gener , illy bears stronger sculpture than does P. m . musicola . A\\ P. m.
fortisculpta examined are rugosely costate . Generally . P. m . musicola is
more weakly sculptured. but this trait is highly variable. Iii a single lot some
specimens may be nearly smooth, while others may be quite strongly COM.Ve.
The two subspecies also differ in the development of the parietal c:illus. P.
m. fortisculpta has a distinct but thin callus. P. m. nmsiCOM has a thilitier .
hardly noticeable parietal deposit.

P. ni . fortisctilpta was previously reported from Mona Island as
Plagiolityclia cticlasta (Shuttleworth) (Clench 1950: 276). Some observations
regarding the systematics of P. nit(sic(}1a (Shuttleworth 1854 ) are
appropriate at this point. P. mtisicola was originally described as a //cll ,
(1·lelicidae), .is were most other helicoid snails at that tillie. Pilsbry
( 1894: 57) placed musicola in Thysanophoriz (Polygyridae). where he
included an heterogenous assortment of unrelated species. Later. Pilsbr>
(1926:112) proposed the genus Stiavitus (Sagdidae) and the subgenus
Euclastaria and designated music'ola as the type species of the latter. Baket
(1943:85) showed that anatomically Eticlastanit is in the X:Iritlionychill:le.
subgenerically related to Plagioptycha .

P. musicola \s divided into three subspecies iii addition to P. m.
fortisculpta: P. m. musicoM (Shuttleworth), P. m . ct K' lasfa (Shuttleworth ),
and P. m . beattyi Clench . P. m. musicola ( Figs . 70 -72) is widely distributed
in Puerto Rico and is typical of wetter and more elevated localities. P. m.
ctidasm (Figs. 66-69) is found along lower. drier coast,11 areits of Piterti,
Rico, St. Thomas, St. Johns. Tortola. mid Vii'que (B,Iker 1961:145). l'e\\
differences occur between the two subspecies. P. m. t'lic·histi, is more
depressed than P. m. musicola. Great overlap occurs in this ch,11.icter ill
some population samples from Puerto Rico and tile Virgin |shmds (vall lier
Schalie 1948:83-84). Clench (1950:276) apparently overlooked \.iii der
Schalie's observations and continiled to treat cuchism its a di>tinct species.
Baker (1961:145) reaffirmed van der Schalie's observations. Ilic third
subspecies. P. m. bea[tyi. is known only froni St . Croix (('lench 1040 : 244 ). It
is characterized by having a depressed shell with an acute|\ £,11 liliate
periphery.



THOMPSON: MONA ISLAND LAND SNAILS 105

ETYMOLOGY.-- The name fortisculpta is from the Latin fortis,
meaning strong, and sculpta, carved, and alludes to the strong sculpture of
this subspecies compared to other subspecies ofPlagioptycha musicola.

LITERATURE CITED

Aaron, J.M. 1975. Geology and mineral resources of IsIa de Mona P.R. Appendix B in
F.H. Wadsworth (ed.). Las Islas de Mona y Monito: Un Evaluaci6n de sus
Recursos Naturales e Hist6ricos. Vols. I, II. Estado Libre Asociado de Puerto
Rico, Oficina deI Gobernador, Junta de Calidad Ambiental.

Adams, C.B. 1849-52. Contributions to Conchology. Bailliere, New York, 258 pp.
Baker H.B. 1924. Land and freshwater molluscs of the Dutch Leeward Islands. Occ. Pap.

Mus. Zoot. Univ. Michigan (152):1-159; pls. 1-21.
. 1928. Mexican mollusks collected for Dr. Bryant Walker in 1926. Pt. I. Occ.

Pap. Mus. Zool. Univ. Michigan (193):1-65; pls. 1-6.
. 1934. Jamaican land snails. Nautilus 48:6-14.

1935. Janiaican land snails, 2. Nautilus 48:84-88.
1935a. Jamaican land snails, 6. Nautilus 49:52-58.

. 1940. Some Antillean Sagdidae and Polygyridae. Nautilus 54:54-62; pls. 4,5.
. 1941. New Puerto Rican land snails  Notulae Naturae (88):1-6.

1943. Some Antillean helicids. Nautilus 56:81-91; pls. 9-11.
. 1961. Puerto Rican Xantlionichidae. Nautilus 74:142-149.
. 1962. Puerto Rican Holopopodes. Nautilus 75:116-121.
. 1962a. Puerto Rican land operculates. Nautilus 76:16-22.

Brcure, A.S.H. 1974. Caribbean land molluscs: Bulimulidae, 1; Bulimulus. Stud. Fauna
Curacao and other Caribbean Islands 45:1-80; pls. 1-8.

C[ench. W. J. 1940. Two new land shells from Puerto Rico and St. Croix. Mcm. Soc.
Cubana Hist. Nat. 14:243-244; pl. 42.

. 1950. Land shells of Mona Island, Puerto Rico. 1. Concliyl. 90:269-276.
Dall, W. H., and C.T. Simpson. 1901. The Mollusca of Puerto Rico. Bull. U.S. Fish. Comm.

(1900) 1:352-524; pls. 53-58.
Pfciffer, L. 1849. Description of twenty-nine new species of Helicitia, from [lie collection (11

H. Cuming, Esq. Proc. Zool. Soc. London for 1848:119-125.
Pilsbry. HA 1894. Manual of Conchology, Ser. I[, 9:i-xlvili, 1-366. pls. 1-71. Phil.idelL,Iiia.

. 1899. Manual of Conchology, Ser. II, 12; 1-258; pls. 1-64. Philadelphia.

. 1903-1904. Manual of Conchology, Ser. [I, 16:i-xi, 1-329; pls. 1-37. ihil.idclphi.i.
1907-1908. Manual of Conchology, Ser. il, 19:i-krvii, 1-333, pls. 1-51

Pliiladelpliia
1926. The land mollusks of [lic Re'lliblic t,IP.iii,itii.i .itid ilic ('.Iii,11/.c,:,·. 1'1·(,c

Acad. Nat. Sci. Philadelphia 78:57-133.
1940. Land Mollusca of Nor[Ii America, Vol. 1, P[. 2. 1\Ic,ilt,gr. Acall. N,,1. Sci.

Philadelphia: 575-994.



106 BULL. FLORIDA STATE MUS., BIOL. SCI. 31(2)

Schalie, H. van der. 1948. The land and freshwater mollusks of Puerto Rico. Misc. Publ.
Mui Zool. Univ. Michigan (70):1-133; pls. 1-14.

Shuttleworth, R.J. 1854. Diagnosen Neuer Mollusken, No. 6. Beitrage zur niiheren
Kenntnis der Land- und Susswasser-Mollusken der Insel Portorico. Bern. Mitth.
Natur. Gesel. : 33-56.

Thompson, F.G. 1976. Land snails.from Monito Island, West Indies. Nautilus 90:152-153.
1982. T'he Helicina umbonata complex in the West Indies (Gastropoda,

Prosobranchia, Helicinidae). Bull. Florida.State Mus., Biol. Sci. 28(1):1-23.
Wadsworth, F.H. 1975. The historical resources of Mona Island. Appendix N in F.H.

Wadsworth (ed.). Las IsIas de Mona y Monito: Un Evaluaci6n de sus Recursos
Naturales e Hist6ricos. Vols. I, II. Estado Libre Asociado de Puerto Rico,
Oficina del Gobernador, Junta de Calidad Ambiental.

Woodbury, R.O. 1975. The vegetation of Mona Island. Appendix G in F.H. Wadsworth
(ed.). Las Islas de Mona y Monito: Un Evaluaci6n de sus Recursos Naturales e
Historicos. Vols. I, II. Estado Libre Asociado de Puerto Rico, Oficina del
Gobernador, Junta de Calidad Ambiental.



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