Tryonia clathrata Stimpson 1865

Tryonia clathrata Stimpson, 1865

Tryonia clathrata Stimpson, 1865:54, pl. 8: fig. 1 [type locality, basin of the Colorado Desert],—Baker, 1964:172 [lectotype selection],—Hershler and Thompson, 1987, figs. 1, 2, 11–15, 19, 21–23; 1992, figs. 71a,c-e, 72.—Hershler, 1999:331–332. fig. 14 [distribution map].

DIAGNOSIS.—Shell medium- to large-sized, conical. Penial ornament of 4 medial to proximal and 1 basal papillae along inner edge, and occasional basal papilla arising from near midline (rather than from penis edge).

DESCRIPTION.—Shell (Figures 4E, 22G) 2.9–7.0 mm tall. Whorls, 5.75–8.75, weakly convex; collabral sculpture varying from low ribs to almost spinose projections, beginning at about 1.5 whorls, becoming strong at whorl 3.0; sculptural elements about 15 on body whorl. Aperture ovate-pyriform, lip complete in larger specimens, thin, adnate; shell imperforate or narrowly umbilicate. Operculum (Figure 6C,F) ellipsoidal, nucleus highly eccentric, inner side smooth. Ctenidial filaments about 42, pleated. Stomach with small posterior caecum. Radula with about 56 rows of teeth; length/width of ribbon 550%. Dorsal edge of central radular teeth (Figure 7D) weakly indented, basal tongue U-shaped, central cusps narrowly pointed, lateral cusps 6–8, basal cusps 2 or 3. Lateral teeth (Figure 8A) with 3 or 4 cusps on inner side and 4–6 cusps on outer side; outer wing strongly flexed, length 150% width of tooth face. Inner marginal teeth with 22–29 cusps, outer marginal teeth with 28–32 cusps.

Prostate gland large, bean-shaped, pallial section 33% of total length. Distal penis pigmented, well-developed swelling on inner edge, penial duct gently undulating (Figure 25E). Oviduct loop posterior-oblique, pigmented. Brood-pouch opening terminal, slightly muscular; brooded embryos about 15. Albumen gland on right side of and partly dorsal to bursa copulatrix. Bursa copulatrix large for genus, ovate; seminal receptacle much smaller than bursa copulatrix, ovate. Sperm-duct opening to proximal portion of bursal duct. Sperm-tube opening in posterior 33%–50% of pallial cavity.

DISTRIBUTION.—White River trough, southern Nevada.

DISTRIBUTION.—Endemic to Ash Meadows, Amargosa River basin, Nevada.

MATERIAL EXAMINED.—UNITED STATES. Nevada: Point of Rocks spring, Nye County, USNM 859159 (holotype), USNM 850309.

Tryonia ericae Hershler and Sada, 1987

Tryonia ericae Hershler and Sada, 1987:826–831, figs. 39c,d, 42f,i, 44, 53a-d, 54, 55, table 2 [type locality, North Scruggs Spring, Ash Meadows, Nye County, Nevada],—Hershler, 1989, table 2.

DIAGNOSIS.—Shell small, conical. Penial ornament of 2 distal and 1 basal to medial papillae along inner edge.

DESCRIPTION.—Shell (Figure 22I) 1.2–1.9 mm tall. Shell apex shown in Figure 5F. Whorls, 3.75–6.0, medium convexity, sutures impressed. Aperture ovate, lip complete, often slightly thickened all around, often separated from body whorl; umbilicus rimate to broadly open. Operculum ovate, whorl edges slightly flared on outer side. Ctenidial filaments about 14, without pleats. Stomach without posterior caecum. Radula with about 42 rows, posteriormost 12 rows weakly developed; length/width of ribbon 410%. Dorsal edge of central radular teeth weakly indented, basal tongue V-shaped, central cusps narrowly pointed, lateral cusps 5 or 6, basal cusps 2. Lateral teeth having 3 cusps on inner side and 4 or 5 cusps on outer side; outer wing weakly flexed, length 175% width of tooth face. Inner marginal teeth with 14–25 cusps, outer marginal teeth with 21–28 cusps.

Prostate gland very small, bean-shaped, pallial section 33% of total length. Distal penis pigmented, weak swelling along inner edge, penial duct with several weak undulations (Figure 26A). Oviduct loop posterior-oblique, pigmented. Brood-pouch opening terminal, slightly raised (Figure 3A); brooded embryos 1 or 2. Albumen gland on right side of bursa copulatrix. Bursa copulatrix large for genus, ovate; seminal receptacle much smaller than bursa copulatrix, globular. Sperm-duct opening to base of bursal duct. Sperm tube long, fused with brood-pouch opening.

DISTRIBUTION.—Endemic to Ash Meadows, Amargosa River basin, Nevada.

The grated tryonia, also known as the White River snail, scientific name Tryonia clathrata, is a species of very small or minute freshwater snail with an operculum, an aquatic gastropod mollusk in the family Hydrobiidae. This species is endemic to the United States.