Brevisentis Hyman, 2007

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 : 44

Brevisentis Hyman, 2007

Brevisentis Hyman, 2007: 93 . Type species Helix jacksoniensis Gray, 1834 (OD).

Description. External morphology: Shell 4.4–4.8 whorls, glossy, spire and apex slightly raised. 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, very narrow U-shape. Mantle laps small to moderately long, not fused, uniform in colour. Mantle lobes small to very small, not fused. Caudal apparatus as for family; caudal foss vertical slit in tail.

Mantle cavity: Mantle with visible minor blood vessels; pigmentation of black and white spots, orange spots in some specimens of B. jacksoniensis .

Digestive system: Oesophageal crop absent.

Genital system: Carrefour embedded in albumen gland; talon shallowly embedded ( B. jacksoniensis ) or free ( B. atratus ). Free oviduct short ( B. atratus ) or short to long ( B. jacksoniensis ); capsular gland present; internal longitudinal pilasters absent. Bursa copulatrix inserted on vagina, short to moderately short, less than or equal to half spermoviduct length; duct of bursa copulatrix wide, distinguishable from bursa copulatrix, internally with longitudinal pilasters. Vagina internally with longitudinal pilasters. Epiphallus enters penis laterally, through short to medium length verge; folded over top of penis and attached by connective tissue. Penis interior variable, consisting of pustules at apical end (sometimes partially fused) and longitudinal ( B. jacksoniensis ) or irregular ( B. atratus ) ridges at basal end; diverticulum on penis absent. Penial sheath enclosing only penis; penis retractor muscle attached to epiphallus. Epiphallus internally with longitudinal pilasters. Epiphallic retractor caecum absent. Flagellum present; flagellum and distal part of epiphallus with internal cryptae forming external projections. Spermatophore soft capsule with firm tail pipe, open at one end; tail pipe short and spiralling, sculptured with moderately short branching spines close to capsule, without sculpture at end of tail.

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

Remarks. This genus was created by Hyman (2007) for two species previously included in Melocystis , the latter genus being placed in synonymy with Nitor . A detailed account of the history of this group and its anatomy is given by Hyman (2007).

Brevisentis differs from all other Australian helicarionid snails in having the short, wide and coiled flagellum, correspondingly spinose spermatophore, absent epiphallic caecum and extremely short vagina seen in the semislug genera Helicarion , Mysticarion , Parmavitrina and Peloparion . Brevisentis can also be readily differentiated externally from Nitor , the only confamilial snail genus with a range overlapping that of Brevisentis , by its rounded whorl profile and longer mantle laps.