Tryonia aequicostata (Pilsbry 1890)

Tryonia aequicostata (Pilsbry, 1890)

Bythinella aequicostata Pilsbry, 1890a:86, pl. III: fig. 16 [type locality, Sumter County, Florida].—Baker, 1964:171 [lectotype selection].

Fontigens oxybeles Pilsbry, 1950:37–38, pl. 3: figs. 1, 1a. 1b [type locality, Silver Spring Run, Lake George, Marion County, Florida].—Thompson, 1968:46 [synonymized with Hyalopyrgus aequicostatus].

Hyalopyrgus aequicostatus.—Thompson, 1968:46–52, figs. 5, 25C, D, 29F, 32B, 39A–F, 49A–E, 59D–F, tables 2, 3 [reassignment; suggested type lot probably from Lake Panasoffkee, Florida].

Tryonia aequicostata.—Hershler and Thompson, 1987:26, figs. 3, 9, 10, 16, 17, 20, 24 [reassignment].

DIAGNOSIS.—Shell medium- to large-sized, conical. Penial ornament of 2 distal papillae along inner edge and an enlarged basal papilla on outer edge.

DESCRIPTION.—Shell (Figures 4G, 22A,B) 3.8–6.0 mm tall. Males much smaller than females (Thompson, 1968, tables 2, 3). Whorls, 4.5–7.5, medium convexity; teleoconch often sculptured with numerous low, collabral varices (up to 20 on body whorl); early portion also often lined with few, regularly spaced spiral lirae. Aperture ovate, lip very thin, incomplete across parietal wall except in largest specimens; shell imperforate or narrowly umbilicate. Operculum ovate, inner side with weak rim along outer edge. Ctendial filaments about 35, pleated. Stomach without posterior caecum. Radula with about 55 rows of teeth, length/width of ribbon 500%. Dorsal edge of central radular teeth well indented, basal tongue broadly V- shaped, central cusps narrowly pointed, lateral cusps 3–6; basal cusps 1 or 2, outer cusps often weakly developed. Lateral teeth having 2–4 cusps on inner side and 4–6 cusps on outer side; outer wing strongly flexed, length 200% width of tooth face; basal tongue weakly developed. Inner marginal teeth with 20–25 cusps, outer marginal teeth with 21–30 cusps.

Prostate gland very small, globular, pallial section 33% of total length. Distal penis pigmented, with pronounced swelling on inner edge, penial duct undulating (Figure 25A). Oviduct loop anterior-oblique, pigmented. Brood-pouch opening terminal, slightly muscularized; posterior portion with additional loop on left side of bursa copulatrix (Figure 3B); brooded embryos about 30, often forming 2 rows in posteriorly folded section. Albumen gland largely dorsal to bursa copulatrix. Bursa copulatrix small, narrowly ovate; seminal receptacle slightly smaller than bursa copulatrix, ovate. Sperm-duct opening to base of bursal duct. Sperm-tube opening in posterior 33% of pallial cavity.

DISTRIBUTION.—Upper Florida peninsula (Atlantic Ocean and Gulf of Mexico coastal drainages).

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

MATERIAL EXAMINED.—UNITED STATES. Nevada: Fairbanks Spring, Nye County, USNM 859151 (holotype), USNM 850299; Big Spring, Ash Meadows, Nye County, USNM 883304.