A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554 35
dium centered slightly posterior to middle of ctenidial axis.
Kidney opening white. Stomach caecum medium-sized.
Testis, 0.75-1.0 whorls, abutting or very slightly overlapping
posterior stomach chamber. Prostate gland with short
pallial section; pallial vas deferens proximally kinked. Penis
(Figure 45/) large; base square; filament slightly shorter than
base, broad; lobe very short, triangular. Penial gland extending
almost to tip of filament. Terminal gland variably shaped,
borne on distal edge of lobe, usually on ventral side. Ventral
gland large, stalked, positioned near base of lobe; second gland
sometimes present lateral (inside) to above. Filament pale to
moderately pigmented.
Ovary, 0.5-0.75 whorls, abutting or slightly overlapping
posterior stomach chamber. Pallial albumen gland large (40%).
Capsule gland about equal to albumen gland in length. Genital
aperture a subterminal slit with short vestibule. Coiled oviduct
a posterior oblique loop well behind pallial wall. Oviduct and
bursal duct join just behind pallial wall. Bursal copulatrix
pyriform, posterior end weakly angled, as long or slightly
longer and almost as broad as albumen gland, with most of
length (90%) posterior to gland. Bursal duct short, narrow,
dorsal to coiled oviduct. Seminal receptacle finger-like, short,
overlapping anterior bursa copulatrix, extending to posterior
edge of albumen gland.
TYPE LOCALITY.—Washington County, Utah (not subsequently
restricted). One of two specimens in type lot (per
Baker, 1964:172) figured by Pilsbry selected herein as
lectotype, ANSP 12112; paralectotypes, ANSP 396958.
DISTRIBUTION.—Virgin River drainage. Consisting of disjunct
groups of populations in and near St. George, southwestern
Utah; and below the Virgin River Narrows near Littlefield,
northwestern Arizona.
REMARKS.—Amongst the group of species whose penis is
ornamented by penial, terminal, and ventral glands, this species
is strongly differentiated by features including a deeply
indented dorsal edge of central radular tooth; simple, circular
oviduct coil, enlarged bursa copulatrix, and dorsally positioned
bursal duct. Pyrgulopsis deserta differs from more advanced
members of Clade 5 by its circular terminal gland and absence
of dorsal glands on the penis.
The two groups of populations are differentiated, with
Arizona snails having smaller, more globose shells.
MATERIAL EXAMINED.—USNM 847202, spring upstream
on Virgin River from Littlefield, Mohave County, Arizona (T
40N, R 15W, sec. 3).
Pyrgulopsis erythropoma (Pilsbry, 1899)
Fluminicola fusca var. minor Stearns, 1893:282 [nomen nudum].
Fluminicola erythropoma Pilsbry, 1899:125.—Hannibal, 1912b:188.—
Walker, 1918:141.—Baker, 1964:172.—Burch, 1982:22.—T\irgeon et al.,
1988:60.
"Fluminicola" erythropoma.—Taylor, 1975:79.
Pyrgulopsis erythropoma.—Hershler and Sada, 1987:791, figs. 8b,e,h, 17,
18d-i, 19b,c, 20-22,23a-c, 24a,c, 25.—USDI, 1991b:58821.
DIAGNOSIS.—Shell globose-turbinate, small to mediumsized,
umbilicate. Penial filament elongate, lobe absent Penial
ornament a large, superficial ventral gland.
DESCRIPTION.—Shell (Figure I4d) globose-turbinate;
height, 1.6-2.4 mm; whorls, 3-4. Protoconch weakly punctate,
with a few weak adapical spiral lines on later portion.
Teleoconch whorls moderately convex, shouldered; sculpture
of strong growth lines. Aperture large, broadly ovate, adnate to
body whorl. Inner lip complete, thickened. Outer lip prosocline.
Umbilicus perforate. Periostracum amber.
Operculum (Figure 14i,/) broadly ovate, amber, nucleus
slightly eccentric; dorsal surface frilled. Attachment scar
margin broadly thickened along inner edge, slightly less
thickened between edge and nucleus; scar along outer edge
faint; callus moderate.
Central radular tooth (Figure 35b) with well-indented dorsal
edge; lateral cusps, 7, narrowly elongate; central cusp pointed,
considerably longer than laterals; basal cusps, 1, short, broadly
triangular, with weak dorsal support Basal process broad,
tongue-like; basal sockets deep. Lateral margins thickened;
neck weak.
Cephalic tentacles pale or light-moderate gray. Snout, foot
moderate gray. Opercular lobe sometimes black along inner
edge (internal) and on sides (epidermal). Neck pale or
moderately pigmented. Pallial roof, visceral coil uniformly
black.
Ctenidial filaments, 18, tall, medium width. Osphradium
small, centered posterior to middle of ctenidial axis. Kidney
opening slightly thickened. Stomach caecum small, narrow.
Testis, 1 whorl, overlapping stomach to edge of style sac.
Prostate gland a fat bean-shape, with large (30%) pallial
section; pallial vas deferens with small proximal kink. Penis
(Figure 46a) medium-sized, blade-like; filament slightly
shorter and narrower than base; lobe absent Ventral gland
large, circular, superficial, near-central. Filament dark.
Ovary, 0.5 whorl, overlapping posterior stomach chamber.
Albumen usually without a pallial section. Capsule gland as
long as albumen gland. Genital aperture a broad, terminal pore,
usually without vestibule. Coiled oviduct a weak twist
followed by near circular loop. Oviduct and bursal duct join
slightly behind pallial wall. Bursa copulatrix globular-ovoid,
short (27%), about half as wide as albumen gland, positioned
largely (66%-75%) posterior to albumen gland. Bursal duct
narrow, about as long as bursa copulatrix. Seminal receptacle
finger-like, medium length, positioned lateral to proximal
bursal duct.
TYPE LOCALITY.—Ash Meadows, Nye County, Nevada.
Original material was collected in 1891 by F. Stephens as
member of the Death Valley Exploring Expedition. According
to the list of collecting localities of the expedition (Palmer,
1893), the Ash Meadows spring visited by Stephens was, "King
Spring or Stone House (altitude about ... 1,160 m), on the
eastern side of the valley..." This corresponds to Kings Pool at