A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554
copulatrix. Seminal receptacle pouch-like, slender, short,
overlapping anterior bursa copulatrix (with small portion of
length posterior to albumen gland) near ventral edge of
albumen gland, extending to posterior edge of albumen gland.
TYPE LOCALITY.—Colorado Desert (Cienega Grande), subfossil.
This and other species described by Gould (with same
type locality) based on material collected in conjunction with
the Pacific Railroad Survey have been attributed to the Salton
Sea area of southeastern California (Henderson, 1936c;
Bequaert and Miller, 1973:203). The sole known Pyrgulopsis
living in this area conforms to Gould's description and
illustration of longinqua and closely resembles at least some of
the Pacific Railroad Survey material originally identified as this
species (although extant snails are smaller than the subfossil
specimens). The status of type material for this species,
however, is unclear. The types referred to by Binney (1865;
catalog number 9220) have not been located although I suspect
that USNM 121121 (originally a 5 specimen lot from Blake, as
was Binney's) could be this lot A possible holotype (MCZ
189153) referred to by Johnson (1964) in fact is P. avernalis
(putative paratypes (MCZ 2106) are a mixture of P. avernalis
and P. carinifera), which has a very different shell from that
described by Gould and which does not occur in the Colorado
Desert although originally incorrectly attributed to the region
by Pilsbry.
DISTRIBUTION.—Salton Sea basin, Riverside County, southeastern
California. Only a single living population is known,
from a small spring in the Salt Creek drainage.
REMARKS.—This species differs from similar P. thermalis in
its more elongate shell, posterior position of male and female
gonad, position of Dgl posterior to penial filament, and
presence of Dg3.
MATERIAL EXAMINED.—USNM 874104, unnamed spring
about 1.5 km west-southwest of Hunters Spring, Riverside
County, California (T 8S, R 1 IE, NE1/4 sec. 14).
Pyrgulopsis manantiali (Hershler, 1985)
Hydrobiinae? incertae sedis.—Taylor, 1966b: 173, fig. 4.
"Stiobia" nsp.—Hershler, 1984:67.
Mexistiobia manantiali Hershler, 1985:47, figs. 10-13.
Pyrgulopsis manantiali.—Hershler and Thompson, 1987:29, fig. 8.
DIAGNOSIS.—Shell globose to broadly conical, small,
broadly umbilicate. Penial filament elongate, lobe short Penial
ornament a horizontal terminal gland.
DESCRIPTION.—Shell (Figure 19a) globose to broadly
conical; height, 1.0-1.25 mm; whorls, 3. Protoconch finely
punctate, with faint suggestion of a few spiral lines on later
portion. Teleoconch whorls moderately convex, sometimes
shouldered; sculpture of strong growth lines. Aperture broadly
lunate, only very slightly angled above, narrowly adnate or
separated (sometimes greatly so) from body whorl. Inner lip
complete, moderately thickened. Outer lip slightly thickened,
prosocline. Umbilicus broadly perforate. Periostracum light
gray, extremely thin.
Operculum (Figure I9b,c) broadly ovate, multispiral, light
amber, nucleus near central; dorsal surface weakly frilled.
Attachment scar margin thickened all around, broadly so
between nucleus and mid-point of inner edge. Early opercular
whorls elevated above ventral surface (as thickened cords);
callus small.
Central radular tooth (Figure 37a) with highly indented
dorsal edge; lateral cusps, 4-6; central cusp pointed, narrow;
basal cusps, 1, elongate, slightly curved, with very weak dorsal
support. Basal process narrow; basal sockets deep. Lateral
margins moderately expanded; neck pronounced.
Cephalic tentacles, snout, foot neck light to dark brownblack.
Opercular lobe light to moderately pigmented along
edges. Pallial roof, visceral coil dark brown-black.
Ctenidial filaments, 12, tall and broad. Osphradium large
(50%), broad, positioned centrally to well posterior to middle
of ctenidial axis. Kidney with very small bulge into pallial
cavity, opening very slightly thickened. Stomach without
caecum.
Testis, 0.5 whorl, very slightly overlapping posterior
stomach. Prostate gland ovate, thin-walled, with large (25%)
pallial section; pallial vas deferens proximally kinked. Penis
(Figure 48a) large; filament elongate, medium width, gently
tapered; lobe short, strongly tapered distally. Terminal gland
small, narrow, horizontal, borne on ventral surface of lobe and
extending from near distal tip onto distal penis. Filament darkly
pigmented internally.
Female genitalia shown in Figure 5d. Ovary, 0.5 whorl,
pressed against posterior edge of stomach. Pallial albumen
gland short Capsule gland slightly shorter than albumen gland,
thin-walled, of a single tissue section. Genital aperture a
terminal, large slit with vestibule. Coiled oviduct a broad
horizontal loop occupying much of anterior albumen gland.
Oviduct and bursal duct join at pallial wall. Bursa copulatrix
finger-like, very short (25%) and narrow (20%), shallowly
embedded in albumen gland, positioned immediately posterior
to pallial wall (well anterior to posterior edge of gland). Bursal
duct extremely short, virtually indistinguishable from bursa.
Seminal receptacle finger-like, as long as bursa copulatrix,
positioned behind oviduct coil (well behind bursa copulatrix).
TYPE LOCALITY.—Small spring, 100 m south of Rio
Mesquites at Tierra Blanca, Cuatro Cie*negas basin, Coahuila,
Mexico.
DISTRIBUTION.—Cuatro Cilnegas basin, Coahuila, Mexico.
REMARKS.—Among species having a penis solely ornamented
by a terminal gland, this snail is strongly differentiated
by its minute size, globose shell, multispiral operculum,
elongate osphradium, posterior position of ovary, and unusually
small and narrow bursa copulatrix having a uniquely
anterior position.
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