A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554 71
filament, extending slightly onto right edge of penis. Dgl
elongate, curving from right edge near base of lobe transversely
across penis, generally raised, usually fused with Dg2; Dg2,
when separate, horizontal, short to medium length; Dg3
narrowly elongate, bome on moderate swelling. Dorsal penis
also with 2-5 small glands in central region (variable in size
and placement, sometimes reduced in number through apparent
fusion) between Dgl-Dg2 and base of lobe. Terminal gland
elongate, transverse, curved, covering distal edge of lobe
(mostly ventral surface). Ventral gland stalked, sub-terminal,
positioned just proximal to lobe; accompained by smaller,
stalked gland (sometimes greatly reduced) just proximal to
above (sometimes with third smaller gland on either side of
above). Filament dark.
Ovary, 0.75-1.0 whorl, slightly overlapping posterior
stomach chamber. Albumen gland without a pallial section.
Capsule gland as long as albumen gland. Genital aperture a
subterminal slit with short vestibule. Coiled oviduct a broad,
open, horizontal loop a moderate distance behind pallial wall.
Oviduct and bursal duct join well behind pallial wall. Bursa
copulatrix pyriform, posterior end pointed, as long or longer
than and almost as wide as (92%) albumen gland, with about
67% of length posterior to gland. Bursal duct narrow
proximally, broadening at junction with oviduct, short. Seminal
receptacle pouch-like, short, overlapping anterior bursa copulatrix,
extending to posterior edge of albumen gland.
TYPE LOCALITY.—Unnamed western spring tributary to
Pine Creek, Birchim Canyon, Owens Valley, Inyo County,
California (T 6S, R 3 IE, SE1/4 sec. 9).
DISTRIBUTION.—Pluvial Owens River drainage, and several
endorheic basins to the east (Deep Springs, Fish Lake, Huntoon
Valleys), California-Nevada.
MATERIAL EXAMINED.—USNM 857941 (paratypes).
Eastern American Species
Pyrgulopsis agarhecta (Thompson, 1970)
Marstonia agarhecta Thompson, 1970:243, figs, la-f, 11.—Thompson,
1977:130, figs. 3b, 23, 24, 25h—Burch, 1982:27, figs. 214, 232—Turgeon
et al., 1988:61.
Pyrgulopsis agarhecta.—Hershler and Thompson, 1987:29.—USDI,
1991b:58821.
DIAGNOSIS.—Shell conical, medium-sized, inner lip usually
incomplete, umbilicate. Penial filament medium length, lobe
short. Penial ornament a variably shaped terminal gland.
DESCRIPTION.—Shell (Figure 21d) conical; height, 2.3-2.7
mm; whorls, 4.5. Early protoconch strongly punctate adapically.
Teleoconch whorls strongly convex, weakly shouldered;
sculpture of faint growth lines and very weak spiral striae.
Aperture ovate, medium-sized, slightly angled above, adnate to
body whorl. Parietal lip usually incomplete or a weak glaze;
columellar lip thin, slightly reflected. Outer lip prosocline.
Umbilicus open. Periostracum light brown.
Operculum (Figure 27e,f) broadly ovate, very thin, light
amber (almost pale), slightly indented along outer edge;
nucleus slightly eccentric; dorsal surface weakly frilled.
Attachment scar margin slightly thickened along inner edge;
callus very weak.
Central radular tooth (Figure 41a) with slightly indented
dorsal edge; lateral cusps, 3-5; central cusp weakly rounded,
broader and longer than laterals; basal cusps, 1 (second, weak
outer cusp sometimes present), elongate, with weak dorsal
support. Basal process rounded, weakly excavated. Lateral
margins slightly thickened; neck near absent.
Head-foot unpigmented. Pallial roof with two black streaks
along edges of ctenidiurn. Streaks darkened and usually
connected anteriorly; streak along osphradial margin short
Dorsal edge of glandular oviduct lined with small black
granules. Testis black.
Ctenidial filaments, 22, tall, narrow. Osphradium elongate
(33%), centered posterior to middle of ctenidial axis. Kidney
opening slightly thickened. Stomach caecum broadly triangular,
large.
Testis, 1.5 whorls, overlapping posterior stomach. Coils of
seminal vesicle extremely thickened, conspicuously overlapping
stomach. Prostate gland ovoid, with short pallial section;
pallial vas deferens simple. Penis (Figure 52a) medium-sized,
extending only slightly beyond mantle edge; base short;
filament medium length, gently tapering; lobe short, broad.
Terminal gland large, variably shaped, bome on ventral surface
of lobe distally. Penis unpigmented.
Ovary, 1 whorl, slightly overlapping posterior stomach.
Pallial albumen gland large (30%). Capsule gland slightly
longer than albumen gland. Genital aperture sub-terminal,
short, with vestibule. Coiled oviduct of two broadly overlapping
horizontal loops just behind pallial wall. Oviduct and
bursal duct join anterior to loop in posterior pallial cavity.
Bursa copulatrix pouch-like, short (28%), narrow (25%),
extending almost to posterior edge of albumen gland; anterior
bursa partly embedded in gland. Bursal duct scarcely narrower
than bursa copulatrix, embedded in albumen gland, more than
twice as long as bursa copulatrix. Seminal receptacle stubby,
short, positioned lateral to proximal bursal duct along ventral
edge of albumen gland.
TYPE LOCALITY.—Bluff Creek, 10.4 miles south-southeast
of Hawkinsville, Pulaski County, Georgia. Holotype, FSM
20528; paratypes, FSM 20569.
DISTRIBUTION.—Known only from the type locality, Ocmulgee
River drainage (Atlantic Coastal; Thompson, 1977, fig.
20).
REMARKS.—This snail differs from similar P. castor and P.
halcyon by its more elongate shell and absence of a ventral
penial gland.
MATERIAL EXAMINED—FSM 189468, FSM 193381 (topotypes).
Pyrgulopsis arga (Thompson, 1977), new combination
Marstonia arga Thompson, 1977:119, figs. la,b, 4f, 6-8. 25b—Burch, 1982:
27, figs. 215, 233.—Turgeon et al., 1988:61.