Pyrgulopsis neomexicana (Pilsbry 1916)

Pyrgulopsis neomexicana (Pilsbry, 1916)

Amnicola neomexicana Pilsbry, 1916:111, pl. 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 Dg1, short Dg2, Dg3 borne on weak swelling; elongate, curved, transverse terminal gland, and two ventral glands.

DESCRIPTION.—Shell (Figure 21d) 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 21 e,f) ellipsoidal, light amber (darker in nuclear region); nucleus highly eccentric; dorsal surface 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 38b) 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. Pallial roof, visceral coil dark brown-black.

Ctenidial filaments, 20, tall, narrow. Osphradium centered slightly posterior to middle of ctenidial axis. Kidney with pronounced (40%) pallial 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. Dg1 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).