A Review of the North American Freshwater Snail Genus Pyrgulopsis

54
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
FIGURE 21.—Western Pyrgulopsis: a-c, P. nanus (a, shell, USNM 859192, 1.7 mm; bjc, opercula, USNM
850354, bars = 0.25 mm, 0.27 mm); d-f, P. neomexicana, USNM 873227 (d, shell, 2.0 mm; e.f. opercula,
bars = 0.25 mm, 0.3 mm).
Pyrgulopsis neomexicana (Pilsbry, 1916)
Amnicola neomexicana Pilsbry, 1916:111, pi. XXX: fig. 4.—Walker, 1918-
135.—Baker, 1964:174.
"Amnicola" neomexicana.—Taylor, 1975:127.
Fontelicella neomexicana.—Burch, 1982:26 fig. 239.—Taylor, 1987:22, fig.
10.—Turgeon et al., 1988:61.
Pyrgulopsis neomexicana.—Hershler and Thompson, 1987:29, 30. USDI
1991a:49646; 1991b:58822.
DIAGNOSIS.—Shell globose to ovate-conic, small to medium-sized,
narrowly umbilicate. Penial filament medium
length, lobe short, broad. Penial ornament an elongate penial
gland, circular-transverse Dgl, short Dg2, Dg3 borne on weak
swelling; elongate, curved, transverse terminal gland, and two
ventral glands.
DESCRIPTION.—Shell (Figure 2Id) globose to ovate-conic;
height, 1.6-2.3 mm; whorls, 3.5-4.5. Protoconch invariably
eroded. Teleoconch whorls slightly convex, strongly shouldered;
sculpture of weak growth lines. Aperture ovate, strongly
angled above, adnate to or slightly separated from body whorl.
Inner lip complete, straight, thickened. Outer lip prosocline,
often strongly sinuate. Umbilicus shallow, rimate. Periostracum
light brown.
Operculum (Figure 2\ef) ellipsoidal, light amber (darker in
nuclear region); nucleus highly eccentric; dorsal surface