Pyrgulopsis manantiali (Hershler 1985)

Pyrgulopsis manantiali (Hershler, 1985)

Hydrobiinae? Incertae sedis.—Taylor, 1966b:173, fig. 4.

“Stiobia” n.sp—Hershler, 1984:67.

Mexistiobia manantiali Hershler, 1985:47, figs. 10–13.

Pyrgulopsis manantiali.—Hershler and Thompson, 1987:29, fig. 8.

DIAGNOSIS.—Shell globose to broadly conical, small, broadly umbilicate. Penial filament elongate, lobe short Penial ornament a horizontal terminal gland.

DESCRIPTION.—Shell (Figure 19a) globose to broadly conical; height, 1.0–1.25 mm; whorls, 3. Protoconch finely punctate, with faint suggestion of a few spiral lines on later portion. Teleoconch whorls moderately convex, sometimes shouldered; sculpture of strong growth lines. Aperture broadly lunate, only very slightly angled above, narrowly adnate or separated (sometimes greatly so) from body whorl. Inner lip complete, moderately thickened. Outer lip slightly thickened, prosocline. Umbilicus broadly perforate. Periostracum light gray, extremely thin.

Operculum (Figure 19b,c) broadly ovate, multispiral, light amber; nucleus near central; dorsal surface weakly frilled. Attachment scar margin thickened all around, broadly so between nucleus and mid-point of inner edge. Early opercular whorls elevated above ventral surface (as thickened cords); callus small.

Central radular tooth (Figure 37a) with highly indented dorsal edge; lateral cusps, 4–6; central cusp pointed, narrow; basal cusps, 1, elongate, slightly curved, with very weak dorsal support. Basal process narrow; basal sockets deep. Lateral margins moderately expanded; neck pronounced.

Cephalic tentacles, snout, foot, neck light to dark brown-black. Opercular lobe light to moderately pigmented along edges. Pallial roof, visceral coil dark brown-black.

Ctenidial filaments, 12, tall and broad. Osphradium large (50%), broad, positioned centrally to well posterior to middle of ctenidial axis. Kidney with very small bulge into pallial cavity, opening very slightly thickened. Stomach without caecum.

Testis, 0.5 whorl, very slightly overlapping posterior stomach. Prostate gland ovate, thin-walled, with large (25%) pallial section; pallial vas deferens proximally kinked. Penis (Figure 48a) large; filament elongate, medium width, gently tapered; lobe short, strongly tapered distally. Terminal gland small, narrow, horizontal, borne on ventral surface of lobe and extending from near distal tip onto distal penis. Filament darkly pigmented internally.

Female genitalia shown in Figure 5d. Ovary, 0.5 whorl, pressed against posterior edge of stomach. Pallial albumen gland short. Capsule gland slightly shorter than albumen gland, thin-walled, of a single tissue section. Genital aperture a terminal, large slit with vestibule. Coiled oviduct a broad horizontal loop occupying much of anterior albumen gland. Oviduct and bursal duct join at pallial wall. Bursa copulatrix finger-like, very short (25%) and narrow (20%), shallowly embedded in albumen gland, positioned immediately posterior to pallial wall (well anterior to posterior edge of gland). Bursal duct extremely short, virtually indistinguishable from bursa. Seminal receptacle finger-like, as long as bursa copulatrix, positioned behind oviduct coil (well behind bursa copulatrix).

TYPE LOCALITY.—Small spring, 100 m south of Rio Mesquites at Tierra Blanca, Cuatro Ciénegas basin, Coahuila, Mexico.

DISTRIBUTION.—Cuatro Ciénegas basin, Coahuila, Mexico.

DISTRIBUTION.—Known only from presumed type locality in Pahranagat Valley, which presumably drained to the Colorado basin in late Cenozoic pluvial periods (Hubbs and Miller, 1948).

MATERIAL EXAMINED.—USNM 873163 (presumed topotypes).