A Review of the North American Freshwater Snail Genus Pyrgulopsis

14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
SPECIES OF QUESTIONABLE STATUS.—Hoyia sheldoni, from
Lake Michigan, also may belong in Pyrgulopsis as its shell is
closely similar to eastern members of this genus. Unfortunately,
only dry shells, albeit live-collected, were available for
this species and details discernable from resuscitated animals
were not sufficient to confidently assess the status of this taxon.
I also have been unable to obtain material for assessment of
generic identity of Amnicola yatesiana, which may have lived
in the San Joaquin Valley, California, during recent times
(Taylor, 1981) and which has been allocated to Savaginius (see
Appendix 2).
Western American Species
Pyrgulopsis aardahli Hershler, 1989
Pyrgulopsis aardahli Hershler, 1989:179, figs. 10-14.
DIAGNOSIS.—Shell ovate to broadly conical, medium-sized,
umbilicate. Penial filament short, lobe very small. Penial
ornament a weak, dot-like Dgl; small, circular terminal gland;
and stalked ventral gland.
DESCRIPTION.—Shell (Figure la) ovate to broadly conical;
height, 2.6-3.4 mm; whorls, 4. Protoconch very weakly
punctate. Teleoconch whorls convex, slightly shouldered;
sculpture of faint growth lines. Aperture ovate, narrowly adnate
to or slightly separated from body whorl. Inner lip complete,
medium thickness; columellar lip very slightly reflected. Outer
lip slightly prosocline. Umbilicus rimate to open. Periostracum
light brown.
Operculum (Figure lb,c) broadly ovate, light amber; nucleus
slightly eccentric; dorsal surface strongly frilled. Attachment
scar margin well thickened all around (broadly so along most of
perimeter). Callus well developed.
Central radular tooth (Figure 32a) with moderately indented
dorsal edge; lateral cusps, S; central cusp rounded, considerably
broader and slightly longer than laterals; basal cusps, 1, short,
narrowly triangular, with moderate dorsal support. Basal
process broad; basal sockets deep. Lateral margins thickened;
neck weak.
Snout dark gray-black; neck variably pigmented. Cephalic
tentacles pale other than a light gray patch proximal to
eyespots. Pigment sometimes concentrated along anterior edge
of foot and margins of opercular lobe. Pallial roof, visceral coil
dark brown-black.
Ctenidial filaments, 23, tall, broad. Osphradium elongate
(33%), centered well posterior to middle of ctenidial axis.
Kidney opening white. Stomach caecum finger-like.
Testis, 1.5 whorls, overlapping stomach to edge of style sac.
Prostate gland bean-shaped to near-circular, pallial section
short. Pallial vas deferens weakly kinked proximally. Penis
(Figure 43a) large, extending slightly beyond mantle edge;
filament short, narrow, tapering; lobe short, narrow (sometimes
absent). Dgl dot-like, sometimes absent, positioned near
mid-line. Terminal gland small, circular-transverse, borne on
ventral surface distally (sometimes absent). Ventral gland
large, elongate, borne on prominent swelling. Proximal penial
filament with dark internal pigment.
Ovary, 1 whorl, overlapping posterior stomach. Pallial
albumen gland short. Capsule gland slightly shorter than
albumen gland. Genital aperture a broad terminal slit with very
short vestibule. Coiled oviduct a short horizontal twist
overlapping a near circular loop. Oviduct and bursal duct join
just behind pallial wall. Bursa copulatrix ovoid, medium length
and width, with about 50% of length posterior to albumen
gland. Bursal duct narrow, slightly shorter than bursa copulatrix,
partly embedded in albumen gland anteriorly. Seminal
receptacle finger-like, usually folded, short, overlapping bursal
duct.
TYPE LOCALITY.—Spring, Bramlette Ranch, Benton Valley,
Mono County, California (T IS, R 32E, SW1/4 sec. 6). Holotype,
USNM 860406; paratypes, USNM 857951.
DISTRIBUTION.—Known only from type locality, upper
Owens River drainage.
REMARKS.—Amongst members of the group of closely
similar species living in Owens Valley, California, this snail
resembles P. giulianii in having a penis with highly reduced
lobe and small, circular terminal gland. It differs in having a
kinked pallial vas deferens and seminal receptacle positioned
lateral to the ventral edge of the albumen gland.
MATERIAL EXAMINED.—USNM 857951 (paratypes).