A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554
weakly frilled. Attachment scar margin slightly thickened all
around, sometimes more broadly so between nucleus and
mid-point of inner edge; callus moderately developed.
Central radular tooth (Figure 38fc) with strongly indented
dorsal edge and highly elongate cusps; lateral cusps, 5; central
cusp pointed, considerably longer than laterals; basal cusps, 1,
medium-sized, with weak dorsal support. Basal process
medium width, highly excavated. Lateral margins very slightly
thickened; neck moderate.
Proximal tentacles, snout moderate to dark brown-black.
Foot similarly pigmented along anterior and posterior edges.
Opercular lobe dark over much of surface. Neck paler than
snout. Pallia! roof, visceral coil dark brown-black.
Ctenidial filaments, 20, tall, narrow. Osphradium centered
slightly posterior to middle of ctenidial axis. Kidney with
pronounced (40%) pallia! bulge; opening white. Stomach with
small triangular caecum.
Testis, 0.5 whorl, ending slightly posterior to stomach.
Prostate gland fat, bean-like, with large pallial section (25%);
pallial vas deferens with proximal loop. Penis (Figure 49c)
large; filament medium length, slender, lobe short, broad.
Penial gland filling most of filament length. Dgl short, circular
to diagonal; Dg2 short, oblique (sometimes accompanied by
glandular dot); Dg3 on weak swelling along base of lobe near
right edge. Terminal gland elongate, transverse, curved, borne
along distal edge of lobe (on both surfaces, often split into two
fragments). Ventral gland sub-terminal, stalked, usually accompanied
by second, smaller gland proximal to above.
Filament weakly pigmented.
Ovary, 1 whorl, abutting posterior edge of stomach. Pallial
albumen gland large (25%). Capsule gland slightly longer than
albumen gland. Genital aperture a terminal slit with vestibule.
Coiled oviduct a broad horizontal loop extending to posterior
edge of albumen gland (slightly overlapping bursa copulatrix).
Oviduct and bursal duct join anterior to oviduct coil near pallial
wall. Bursa copulatrix elongate-pyriform, as long as (or slightly
longer than) and as wide as albumen gland, with almost entire
length (90%) posterior to gland. Bursa duct narrow, very short,
emerging slightly posterior to anterior tip of bursa. Seminal
receptacle sac-like, elongate, overlapping bursa copulatrix,
extending to posterior edge of albumen gland.
TYPE LOCALITY.—Socorro [Socorro County], New Mexico,
in warm springs. Lectotype (Baker, 1964:174), ANSP 12113;
paralectotypes, ANSP 396954.
DISTRIBUTION.—Historically confined to several springs in
the Rio Grande drainage of southern New Mexico. Now extinct
at type locality area (Taylor, 1987), and represented by only a
single living population at Torreon Springs.
MATERIAL EXAMINED.—USNM 873227, Torreon Springs,
Socorro County, New Mexico (T 5S, R 2W, NE1/4 sec. 8).
Pyrgulopsis nevadensis (Stearns, 1883)
Pyrgula nevadensis Stearns, 1883:173 [unlabeled figure, p. 173; not Fluminicola
nevadensis Walker, 1916].—Call, 1884:21.—Call and Beecher, 1884:
851, figs. 1-5.—Baker, 1964:174.
Pyrgulopsis nevadensis—Call and Pilsbry, 1886:10, pi. II: figs. 1-10.—
Ancey, 1888:189.—Pilsbry, 1891c:329; 1899:122.—Hannibal,
1912b:189.—Walker, 1918:30, figs. 101, 102.—Thiele, 1928:378.—Wenz,
1939:558, fig. 1499.—Gregg, 1945:69.—Berry, 1947:77, pi. 7: fig.
7.—Baily and Baily, 1951:52, pi. 4: fig. 9—Jacobson, 1952a:15.—Taylor,
1960a:327; 1970:33; 1975:127-128.—Burch, 1982:28, figs. 256, 270-
272.—Hershler and Thompson, 1987:28, figs. 4, 25-29.—Turgeon et al.,
1988:62.
Pyrgalopsis [sic] nevadensis.—Brues, 1932:278.
Pyrgulopsis nevadensis var. ecarinata Ancey, 1888:189.
Pyrgulopsis nevadensis paiutica Baily and Baily, 1951:52, pi. 4: fig. 10, right
figure—Jacobson, 1952a:16; 1952b:70.—Burch, 1982:28.
Pyrgulopsis paiutica.—Baker, 1964:175.
DIAGNOSIS.—Shell ovate-conic to turriform, usually basally
carinate, medium to large-sized, weakly umbilicate. Penial
filament medium length, lobe short Penial ornament a small
terminal gland, and ventral gland.
DESCRIPTION.—Shell (Figure 22a,b) ovate-conic to turriform;
height, 3.5-5.7 mm; whorls, 4.5-6.0. Protoconch
appearing near smooth, but usually eroded. Apical whorls well
rounded, late teleoconch whorls much less so, sometimes
shouldered; sculpture of strong growth lines. Strong peripheral
carina usually present from beginning of third whorl to
aperture, but carina development varying to weak cord or very
slight angulation. Aperture ovate, broadly adnate to body
whorl. Inner lip complete, thin. Outer lip prosocline. Umbilicus
absent to narrowly rimate. Periostracum light brown.
Operculum (Figure 22c,d) ovate, light amber, nucleus
slightly eccentric; dorsal surface smooth. Attachment scar
margin near smooth, with only faint trace between nucleus and
inner edge; central callus weak.
Central radular tooth (Figure 38c) with moderately indented
dorsal edge; lateral cusps, 4-5; central cusp rounded to weakly
pointed, considerably broader and longer than laterals; basal
cusps, 1 (although occasional weak suggestion of second cusp),
elongate, with strong dorsal support Basal process medium
width; basal sockets deep. Lateral margins thickened; neck
absent
Penis (Figure 49d) small (retracted specimens); filament
medium length, narrow; lobe shorter than filament Terminal
gland small, borne along distal edge of lobe (on both surfaces).
Ventral gland large, positioned near distal edge of penis.
Filament pigmented.
TYPE LOCALITY.—Pyrgulopsis nevadensis: Walker and
Pyramid Lakes, Nevada. Subsequently restricted to Pyramid
Lake, Washoe County, Nevada (per Baker, 1964:174). Lectotype,
ANSP 27811; paratypes, ANSP 375739. Pyrgulopsis
ecarinata: Walker and Pyramid Lakes (not restricted subsequently).
Location of types not known. Pyrgulopsis pauitica:
Pyramid Lake, Nevada. Holotype, ANSP 187693; paratypes
ANSP 396956.
DISTRIBUTION.—Pyramid Lake (Recent); Walker Lake,
Winnemucca Lake (Pleistocene?). The snail persisted in
Pyramid Lake at least until the very late 1800s, as evidenced by
presence in museum collections of numerous live-collected
specimens from this period. Recent dredging hauls from the
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