Periclocystis Iredale, 1937

Hyman, Isabel T. & Ponder, Winston F., 2010, A morphological phylogenetic analysis and generic revision of Australian Helicarionidae (Gastropoda: Pulmonata: Stylommatophora), and an assessment of the relationships of the family 2462, Zootaxa 2462 (1), pp. 1-148 : 76-77

Periclocystis Iredale, 1937

Periclocystis Iredale, 1937a: 28 . Type species Periclocystis ardeni Iredale, 1937 (OD).

Description. External morphology: Shell 4.2–4.3 whorls, not glossy, spire and apex flattened, last whorl rapidly descending. Protoconch sculptured with incised spiral grooves; teleoconch with microscopic spiral grooves. Whorl profile rounded above and below evenly convex periphery. Internal walls of early whorls complete; umbilicus open, narrow U-shape. Mantle laps narrow, finger-shaped, very small, not fused, uniform in colour. Mantle lobes very small. Caudal apparatus as for family; caudal foss vertical slit in tail.

Mantle cavity: As for family. Mantle with no visible minor blood vessels; pigmentation of black and white spots.

Digestive system: Oesophageal crop absent.

Genital system: As for family. Carrefour and talon not examined. Free oviduct very long; capsular gland not examined; internal sculpture not examined. Bursa copulatrix inserted on vagina, moderately short, about half spermoviduct length; duct of bursa copulatrix wide, distinguishable from bursa copulatrix, interior not examined. Epiphallus enters penis through simple pore; penis internally covered in flat, ridged, diamondshaped pustules, pilasters absent, diverticulum on penis absent. Penial sheath thick, enclosing only penis; penis retractor muscle attached to epiphallus. Epiphallus internally with longitudinal pilasters. Epiphallic retractor caecum absent. Very short lime-sac present. Spermatophore not present in dissected material.

Radula: Not examined.

Remarks. Periclocystis , like Echonitor , is restricted to South Australia. This monotypic genus was separated from Echonitor on the basis of a more flattened shell, dull rather than glossy, with a slightly wider umbilicus and a small, thick, non-reflected columella. No description of the anatomy has been previously published.

Periclocystis shares with five other genera ( Echonitor , Tarocystis , Sheaia , Levidens ) the lack of a flagellum and epiphallic caecum but can be distinguished by the flattened, non-glossy shell with a descending last whorl and the distinctive diamond-shaped, ridged pustules covering the inside of the penis.