Parmavitrina Iredale, 1937c: 8. Type species Helicarion planilabris Cox, 1866 (M).

Description. External morphology: Shell reduced, 3.2–3.5 whorls, glossy, spire and apex flattened. 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 incomplete; base of last whorl membranous; umbilicus not visible. Mantle laps small to medium, rounded, not fused, uniform in colour. Mantle lobes small to medium, left and median mantle lobes fused. Sole of foot and caudal apparatus as for family; caudal horn small; caudal foss vertical slit in tail.

Mantle cavity: As for family. Mantle with visible minor blood vessels, pigmentation absent.

Digestive system: Oesophageal crop present (separated from stomach only by a slight constriction).

Genital system: As for family. Free oviduct long; capsular gland present; internal longitudinal pilasters absent. Bursa copulatrix inserted on vagina, short, less than half spermoviduct length; duct of bursa copulatrix wide, distinguishable from bursa copulatrix, internally with longitudinal pilasters. Vagina very short. Epiphallus enters penis through simple pore; penis internally smooth, longitudinal penis pilasters present, penial diverticulum absent. Penial sheath present, enclosing only base of penis; penis retractor muscle attached to epiphallus. Epiphallus internally with wavy longitudinal pilasters. Epiphallic retractor caecum absent. Flagellum present; flagellum and distal part of epiphallus with internal cryptae forming numerous external projections. Spermatophore not seen in dissected specimens.

Radula: Relatively long and narrow. Central tooth with small ectocones; mesocone lanceolate, shorter than tooth base. Lateral and marginal tooth fields distinguishable. Lateral teeth with endocone much smaller than central tooth ectocones; ectocone equal in size to those on central tooth; mesocone approximately equal in length to tooth base. Marginal teeth with endocones absent; ectocones shorter and narrower than the mesocone, not subdivided into extra teeth.

Remarks. Parmavitrina was originally described as a monotypic subgenus of Helicarion (Iredale 1937c). Iredale (1937c) listed Vitrina megastoma Cox, 1868 as a synonym of Parmavitrina planilabris but it was treated as valid by Smith (1992) who listed both species. No anatomical data was previously available on either species.

Only Parmavitrina planilabris is described in the current study; however, external features of P. megastoma have been examined and are included in the generic description. There is at least one undescribed species known in this genus; photographs of P. megastoma and an undescribed species from mid-coastal New South Wales (northern Sydney to Bulahdelah) are shown in Figure 6D–E.