A Review of the North American Freshwater Snail Genus Pyrgulopsis

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ventral gland.
DESCRIPTION.—Shell (Figure 24a) globose to broadly
conical; height, 1.8-2.7 mm; whorls, 3.25-4.5. Early protoconch
finely punctate, otherwise smooth except for weak spiral
lines, leleoconch whorls moderately convex, shouldered;
sculpture of strong growth lines and occasionally numerous
faint spiral striae. Aperture narrowly adnate to or slightly
separated from body whorl. Inner lip complete, thickened;
columellar lip slightly reflected. Outer lip prosocline, weakly
sinuate. Umbilicus perforate. Periostracum light brown, very
thin, often absent
Operculum (Figure 24b,c) broadly ovate, amber, nucleus
slightly eccentric; dorsal surface frilled. Attachment scar
margin moderately thickened all around, broadly so along inner
edge near nucleus; callus moderately developed.
Central radular tooth (Figure 39ft) with weakly indented
dorsal edge; lateral cusps, 3-4; central cusp pointed, much
longer and broader than laterals; basal cusps, 1, medium-sized,
with weak dorsal support Basal process narrow; basal sockets
deep. Lateral margins thickened; neck moderate.
Cephalic tentacles, neck pale to dark brown. Snout, foot
pigment moderate to dark brown. Opercular lobe dark along
inner edge. Pallial roof, visceral coil dark, uniform brownblack.
Ctenidial filaments, 21, very tall, medium width. Osphradium
centered well posterior to middle of ctenidial axis.
Kidney opening slightly thickened. Stomach caecum absent
Testis, 1.5 whorls, overlapping anterior stomach chamber
almost to edge of style sac. Prostate gland with short pallial
section; pallial vas deferens with prominent proximal kink.
Penis (Figure 50c) medium-sized; filament medium length,
narrow, tapering; lobe absent or a slight bulge. Ventral gland
large, circular, superficial, positioned close to left edge near
mid-length. Filament dark.
Ovary, 1 whorl, overlapping posterior stomach chamber.
Albumen gland without a pallial section. Capsule gland as long
as albumen gland. Genital aperture a short terminal slit with
very short vestibule. Coiled oviduct a horizontal loop slightly
behind pallial wall. Oviduct and bursal duct join just behind
pallial wall. Bursa copulatrix near globular, short (30%),
medium width, with 25%-50% of length posterior to gland.
Anterior bursa copulatrix sometimes embedded in albumen
gland. Bursal duct very narrow, (deeply) embedded in albumen
gland anteriorly, longer than bursa copulatrix. Seminal receptacle
sac-like, narrow, often folded, short, positioned just anterior
to or very slightly overlapping bursa copulatrix.
TYPE LOCALITY.—Marsh Spring, Ash Meadows, Nye
County, Nevada (T 17S, R 50E, SE1/4 sec. 35). Holotype,
USNM 859197; paratypes, USNM 859198, FSM 94958.
DISTRIBUTION.—Ash Meadows, Amargosa River drainage.
MATERIAL EXAMINED.—USNM 850363, 850364 (topotypes).
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
Pyrgulopsis robusta (Walker, 1908)
Pomatiopsis robusta Walker, 1908:97 [unlabeled figure]; 1918:148.—
Henderson, 1918:41; 1924:192; 1932:133; 1933:1.—Baker, 1928:162.—
Abbott 1948:66.
Amnicola robusta.—Pilsbry 1933:9, pi. 2: figs. 1, 7, 8.—Henderson, 1936a:
137, fig. 7.—Beetle, 1957:17; 1961:5.
Fontelicella (Natricola) robusta—Oregg and Taylor, 1965:109.—Burch,
1982:26, figs. 230,243.
Fontelicella robusta—Taylor, 1975:167.—Beetle, 1989:639.—Turgeonet al.,
1988:61.
Pyrgulopsis robusta.—HersMer and Thompson, 1987:30.—USDI,
1991b:58822.
DIAGNOSIS.—Shell ovate- to narrowly-conic, large, umbilicate.
Penial filament medium length; lobe medium length,
broad. Penial ornament an elongate Dgl, short Dg2; small Dg3,
sometimes absent, borne on lobule; elongate, transverse,
slightly curved terminal gland; and ventral gland.
DESCRIPTION.—Shell (Figure 24c/) ovate- to narrowly-conic;
height, 5.5-6.3 mm; whorls, 5.0-5.5. Protoconch with small,
very weakly punctate area near apex, otherwise smooth except
for faint suggestion of spiral striae adapically. leleoconch
whorls moderately convex, shouldered; sculpture of weak
growth lines. Aperture adnate to very slightly separated from
body whorl. Inner lip complete, thickened. Outer lip slightly
thinner, prosocline. Umbilicus narrowly rimate to perforate.
Periostracum thick, brown.
Operculum (Figure 24e,f) ovate, amber, darker centrally;
nucleus slightly eccentric; dorsal surface frilled. Attachment
scar margin moderately thickened almost all around, sometimes
broadly so along inner edge and between edge and
nucleus; callus moderate-strongly developed.
Central radular tooth (Figure 39c) with weakly indented
dorsal edge; lateral cusps, 5-6; central cusp rounded, much
longer, slightly broader than laterals; basal cusps, 1, small,
curved, with strong dorsal support. Basal process very broad;
basal sockets deep. Lateral margins thickened; neck moderate.
Cephalic tentacles pale except for small internal pigment
patch just distal to eyespots. Snout light to dark gray-brown.
Foot pale-dark gray. Opercular lobe pale or with small patch of
internal pigment along inner edge. Neck pale except for central
patch of internal pigment. Pallial roof, visceral coil black.
Ctenidial filaments, 32, tall, very broad. Osphradium
centered slightly posterior to middle of ctenidial axis. Kidney
opening white. Stomach caecum large, broadly triangular.
Testis, 1.75 whorls, overlapping stomach to edge of style
sac. Prostate gland with large (40%) pallial section; pallial vas
deferens with proximal kink. Penis (Figure 50d) large; base
broadly rectangular, filament medium length, narrow, tapering;
lobe about as long as filament, stout. Dgl elongate, extending
from base of filament (slightly overlapped) along right edge,
posterior portion curving inward, slightly raised; Dg2 short,
horizontal or tilted toward Dg3, sometimes broken into two