Tryonia hertleini (Drake 1956)

Tryonia hertleini (Drake, 1956)

Lyrodes hertleini Drake, 1956:44–46, pl. 15 [type locality, springs at Las Palomas, Chihuahua, Mexico].

Fontelicella hertleini.—Taylor, 1975:95 [reassignment].

Tryonia hertleini.—Hershler and Thompson, 1992:110 [reassignment].

DIAGNOSIS.—Shell medium-sized, conical. Penial ornament of 2 distal and 1 massive basal papillae on inner edge.

DESCRIPTION.—Shell (Figures 4D, 23D) 2.5–3.2 mm tall. Whorls, 4.75–5.5, medium convexity; teleoconch sculptured with a few spiral lines. Aperture ovate, lip complete, thin, adnate; shell imperforate or narrowly umbilicate. Operculum ovate, inner side smooth. Ctenidial filaments about 33, pleated. Stomach without posterior caecum. Radula with about 36 rows of teeth, the posteriormost 10 weakly developed; length/width of ribbon 460%. Dorsal edge of central radular teeth weakly indented, basal tongue broadly V-shaped, central cusps narrowly pointed, lateral cusps 4 or 5, basal cusps 2. Lateral teeth with 2 cusps on inner side and 4 or 5 cusps on outer side; outer wing strongly flexed, length 260% of tooth-face width. Inner marginal teeth with 15–17 cusps, outer marginal teeth with 26–32 cusps.

Prostate gland large, thick, subglobose, pallial section 33% of total length. Distal penis without pigment, well-developed swelling along inner edge, penial duct undulating (Figure 26D). Oviduct loop anterior-oblique, pigmented. Brood-pouch opening terminal, slightly thickened; brooded embryos about 18, forming 2 rows in posteriorly folded section. Albumen gland on right side of bursa copulatrix. Bursa copulatrix large for genus, ovate; seminal receptacle much smaller than bursa copulatrix, ovate. Sperm-duct opening to distal portion of bursal duct. Sperm-tube opening to posterior 33% of pallial cavity.

DISTRIBUTION.—Las Palomas, interior drainage of northeast Mexico. This species may be extinct because its only known locality dried more than 25 years ago (Landye in Hershler, 1994).