A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554 23
DISTRIBUTION.—This presumably extinct species apparently
was endemic to the type locality, which occurs in the portion of
northwest Chihuahua known as the "Guzmdn complex,"
comprising the terminus of Rfos Mimbres, Casas Grandes,
Santa Maria, and del Carmen (Miller, 1978,1981). The springs
at Las Palomas dried during the 1970s (Jerry Landye, pers.
comm., 1992).
REMARKS.—This snail is united with P. bruneauensis by
unique synapomorphies of a complex oviduct coil (51-2) and
anterior position of seminal receptacle relative to oviduct coil
(61-1). Pyrgulopsis brandi differs by its stronger operculum
attachment scar, larger terminal gland, and elongate seminal
receptacle duct.
MATERIAL EXAMINED.—UMMZ uncat. (M50-8), springfed
pond 3.6 mi. (5.8 km) south of Las Palomas. This is almost
certainly the type locality (despite the discrepancy with Drake's
data) as only a single spring has been known historically from
the area (J. Landye, pers. comm., 1992).
Pyrgulopsis bruneauensis Hershler, 1990
Pyrgulopsis bruneauensis Hershler, 1990:803—USDI, 1993:5938.
Genus and species undescribed.—USDI, 1991b:58818.
DIAGNOSIS.—Shell globose to broadly conical, mediumsized,
umbilicate. Penial filament elongate, lobe very short
Penial ornament a small, weakly developed terminal gland
DESCRIPTION.—Shell (Figure 10a) globose to broadly
conical; height, 2.2-2.9 mm; whorls, 3.75-4.25. Early
protoconch weakly punctate adapically, otherwise near smooth
(often eroded). Teleoconch whorls convex, shouldered; sculpture
of moderately pronounced growth lines. Aperture broadly
ovate, large, very narrowly adnate or (more commonly) slightly
separated from body whorl. Inner lip complete, thick. Outer lip
prosocline. Umbilicus rimate to broadly perforate. Periostracum
light amber.
Operculum (Figure l0b,c) ovate, amber, nucleus slightly
eccentric; dorsal surface weakly frilled. Attachment scar
weakly thickened along inner edge near nucleus, very faint
otherwise; callus a very weak, narrow thickening near inner
edge.
Central radular tooth (Figure 33c) with moderately indented
dorsal edge; lateral cusps, 4-6; central cusp pointed, slightly
broader and considerably longer than laterals; basal cusps, 1,
narrowly triangular, with very weak dorsal support Basal
process broad, tongue-like; basal sockets deep. Lateral margins
thickened; neck pronounced.
Snout dark brown-black; cephalic tentacles similarly pigmented,
although pale around eyespots. Foot pigment moderate-dark,
especially along anterior edge. Opercular lobe black
along sides, with internal black granules concentrated along
inner edge. Neck pigment light-moderate, often with central
pale area extending to foot Pallial roof, visceral coil dark,
near-uniformly pigmented.
Ctenidial filaments, 20, tall, narrow. Osphradium centered
posterior to middle of ctenidial axis. Kidney opening slightly
thickened. Stomach caecum very small.
Testis, 1 whorl, overlapping posterior stomach chamber.
Prostate gland with large (32%) pallial section; pallial vas
deferens proximally kinked. Penis (Figure 44c) medium to
large-sized; filament elongate (about twice as long as base),
muscular, little tapered; lobe very short, slightly tapered
distally. Terminal gland small (sometimes very reduced or
absent), variably shaped, borne along distal edge, usually in
ventral position. Filament very dark (internal pigment).
Female genitalia shown in Figure 5a. Ovary, 0.75 whorl,
overlapping posterior stomach chamber. Pallial albumen gland
large (25%). Capsule gland as long as albumen gland. Genital
aperture a subterminal slit (slightly raised and thickened) with
vestibule. Coiled oviduct usually of three loops (vertical,
posterior oblique, horizontal). Oviduct and bursal duct join
slightly behind pallial wall. Bursa copulatrix ovoid, medium
length and width, with about half of length posterior to gland.
Bursal duct medium width, about as long as bursa copulatrix.
Seminal receptacle stout, short, with short duct pressed against
middle loop of coiled oviduct, usually overlapping anterior
bursa copulatrix or proximal section of bursal duct
TYPE LOCALITY.—Spring along west side of Bruneau River,
about 100 m downflow from Hot Creek's confluence with the
river, Owyhee County, Idaho (T 7S, R 6E, SW1/4 sec. 34).
Holotype, USNM 860507; paratypes, USNM 860508.
DISTRIBUTION.—Small springs along Hot Creek and confluent
Bruneau River, Owyhee County, Snake-Columbia River
basin.
MATERIAL EXAMINED.—USNM 860508 (paratypes).
Pyrgulopsis bryantwalkeri, new name
Fluminicola nevadensis Walker, 1916:6 [unlabeled figure, p. 6 (not Pyrgula
nevadensis Steams, 1883)]; 1918:142.—Turgeonetal., 1988:60.
"Fluminicola" nevadensis.—Taylor, 1975:127.
DIAGNOSIS.—Shell globose to ovate-conic, small to medium-sized,
umbilicate. Penial filament short, lobe very weak.
Penial ornament a weakly developed terminal gland.
DESCRIPTION.—Shell (Figure lOd) globose to ovate-conic;
height 1.5-3.2 mm; whorls, 3.5-4.5. Protoconch moderately
punctate, although weaker near beginning of teleoconch.
Teleoconch whorls moderate to highly convex, shouldered;
body whorl sometimes with weak angulation at or near
periphery; sculpture of weak to strong growth lines. Aperture
broadly ovate, angled above, usually separated (sometimes
greatly so) from body whorl. Inner lip complete, thickened;
columellar region narrowly excavated. Outer lip prosocline.
Umbilicus deeply perforate. Periostracum brown.
Operculum (Figure 10e,/) broadly ovate, dark amber,