A Review of the North American Freshwater Snail Genus Pyrgulopsis

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moderately broad, medium length. Seminal receptacle pouchlike,
short, partly overlapping (or slightly lateral to) anterior
bursa copulatrix.
TYPE LOCALITY.—Small spring in Oasis Valley [Nye
County], Nevada. Lectotype (Baker, 1964:174), ANSP 67279;
paralectotypes, ANSP 368399, USNM 123622.
DISTRIBUTION.—Widespread in southeastern California and
southwestern Nevada: Death Valley system, Mohave River
drainage, small endorheic basins.
REMARKS.—Pyrgulopsis micrococcus is distinguished from
closely similar P. stearnsiana by its larger penial lobe, weak
operculum attachment scar, absence of a pallial section of
albumen gland, and position of bursal duct lateral to albumen
gland.
MATERIAL EXAMINED.—USNM 847246, unnamed springs
comprising headwaters of Amargosa River, Springdale, Nye
County, Nevada (T 10S, R 47E, NE1/4 sec. 31).
Pyrgulopsis montezumensis Hershler, 1988
Amnicola palomasensis.—Smith, 1953:9.
Pyrgulopsis montezumensis Hershler in Hershler and Landye, 1988:23, figs.
lOg, 13a,d, 21a-c, 22, 23.—USDL 1991b:58821.
DIAGNOSIS.—Shell ovate-conic, small to medium-sized,
umbilicate. Penial filament short, lobe very short. Penial
ornament an elongate Dgl, straight terminal gland, and ventral
gland.
DESCRIPTION.—Shell (Figure 20d) ovate-conic; height,
1.7-2.7 mm; whorls, 3.5-4.5. Early protoconch (Figure Id)
moderately punctate adapically, otherwise weakly punctate.
Teleoconch whorls highly convex, shouldered; sculpture of
weak growth lines. Aperture broadly adnate to slightly
separated from body whorl. Inner lip complete, sometimes very
slightly thickened. Outer lip near orthocline. Umbilicus
perforate. Periostracum amber.
Operculum (Figure 20e,f) ovate, light amber, nucleus
slightly eccentric; dorsal surface weakly frilled. Attachment
scar margin thickened all around, broadly so along inner edge;
callus moderately developed.
Central radular tooth (Figure 37e) with moderately indented
dorsal edge; lateral cusps, 6-8; central cusp pointed, considerably
longer than laterals; basal cusps, 1, small, with moderate
dorsal support Basal process moderately broad; basal sockets
deep. Lateral margins thickened; neck pronounced.
Cephalic tentacles, foot, neck pale. Snout near pale to dark
purple-black. Opercular lobe pale or lightly pigmented along
sides. Pallial roof, visceral coil light to dark.
Ctenidial filaments, 20, tall, medium width. Osphradium
centered slightly posterior to middle of ctenidial axis. Kidney
opening slightly thickened. Stomach caecum prominent.
Testis, 1.5 whorls, overlapping posterior stomach chamber.
Prostate gland with short pallial section; pallial vas deferens
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
with strong proximal kink. Penis (Figure 48*) large; filament
short, slender, tapering; lobe very short, broad. Dgl extending
along left edge from near-mid length onto proximal filament
(sometimes absent); Dg2 short-elongate, horizontal. Terminal
gland medium-sized, often transverse, near straight, borne
distally (largely on ventral surface). Ventral gland small,
stalked, near distal edge (sometimes reduced-absent). Filament
usually unpigmented.
Ovary, 0.5 whorl, very slightly overlapping posterior
stomach chamber. Pallial albumen gland large (33%). Capsule
gland as long as albumen gland. Genital aperture a subterminal
slit with short vestibule. Coiled oviduct a broad horizontal loop
positioned slightly behind pallial wall. Oviduct and bursal duct
join just behind pallial wall. Bursa copulatrix ovoid, medium
length and width, with about half of length posterior to gland.
Bursal duct very narrow, shallowly embedded in albumen
gland, about as long as buras copulatrix. Seminal receptacle
sac-like, narrow, short, overlapping anterior bursa copulatrix.
TYPE LOCALITY.—Montezuma Well, Yavapai County, Arizona
(T 15N, R 6E, NW1/4 sec. 31). Holotype, USNM 859043;
paratypes, USNM 859044.
DISTRIBUTION.—Endemic to type locality, Verde River
drainage.
MATERIAL EXAMINED.—USNM 847233 (topotypes).
Pyrgulopsis morrisoni Hershler, 1988
Pyrgulopsis morrisoni Hershler in Hershler and Landye, 1988:21, figs. lOf,
16e-h, 19, 20.—USDI, 1991b:58821.
DIAGNOSIS.—Shell ovate-conic, small to medium-sized,
weakly umbilicate. Penial filament medium length, lobe
elongate. Penial ornament a short, straight terminal gland.
DESCRIPTION.—Shell (Figure 20g) ovate-conic; height,
1.8-2.9 mm; whorls, 3.74-4.5. Protoconch moderately punctate.
Teleoconch whorls moderately convex, often shouldered;
sculpture of weak-moderate growth lines. Aperture broadly
adnate to body whorl (rarely separated). Inner lip complete,
slightly thickened; columellar lip slightly reflected. Outer lip
orthocline to slightly prosocline. Umbicilus narrowly rimate
(rarely absent) to weakly perforate. Periostracum light amber to
brown.
Operculum (Figure 20h,i) broadly ovate, very light amber,
nucleus slightly eccentric; dorsal surface smooth. Attachment
scar margin moderately thickened between nucleus and
mid-point of inner edge; callus moderately developed.
Central radular tooth (Figure 37/) with moderately indented
dorsal edge; lateral cusps, 5-7; central cusp pointed, broader
and considerably longer than laterals; basal cusps, 1, large, with
strong dorsal support. Basal process medium width; basal
sockets deep. Lateral margins thickened; neck pronounced.
Cephalic tentacles pale or with dark pigment patch just distal
to eyespots. Snout, foot pale-light brown. Opercular lobe pale