Brevisentis jacksoniensis (Gray, 1834)
Fig. 9. Live specimens of Brevisentis. A-B. B. atratus: A. AM C.517469, Camden. B. AM C.403813, Coolah Tops National Park. C. B. kaputarensis, QM MO78908, Mt Kaputar. Scale bars = approx. 10 mm.
Helix (Microcystis) jacksoniensis: Cox, 1868: 7, pl. 9, fig. 6.
Nanina (Microcystis) jacksoniensis: Pfeiffer and Clessin, 1881: 36.
Nanina (Subg. Xesta Sect. Microcystis) jacksoniensis: Tryon, 1886: 113, pl. 37, fig. 21.
Nanina (Microchlamys) jacksoniensis: Cox, 1909: 7.
Melocystis jacksoniensis: Iredale, 1937a: 5.
Expocystis exclusus Iredale, 1941: 4, fig. 7.
Melocystis exclusus: Smith, 1992: 238.
Material examined. Types. 2 syntypes of Helix jacksoniensis Gray, 1834 (NHMUK 20160421, Port Jackson, leg. Lamb; Fig. 7A), holotype of Expocystis exclusus Iredale, 1937 AM C.101143, Broken Bay, N of Sydney; Fig. 7B).
Non-type material. See Table S1. Additional material: AM C.319501, AM C.348670, AM C.356645, AM C.162857, AM C.320010.
Diagnosis. Shell. Medium-sized, 4.65-5.25 whorls, amber to golden brown, depressedly subglogose with a low spire; whorls rounded, sutures impressed; protoconch with fine spiral grooves, teleoconch with fine spiral grooves becoming pustulose towards the last whorl. Umbilicus narrow (Table 3, Figs 7A-B, 8A-C).
Table 3. Shell dimensions. Abbreviations: n = number of measured specimens, SH = shell height, SD = shell diameter, NW = number of whorls, AH = aperture height, AW = aperture width.
Animal. Grey with red mucus (staining body red); sole with a slightly paler mid field; caudal gland small. Mantle lobes moderately small, not fused; shell lappets narrow, triangular, right lappet moderately long, left lappet moderately short (Fig. 9A-B).
Genitalia. Penis moderately short, enclosed in penial tunica, slightly swollen at proximal end. Penis interior with longitudinal pilasters at distal end, breaking up into pustules at proximal end. Epiphallus relatively short, approximately 1.5 times penis length, entering penis apically or slightly to one side through rounded, pustulose verge of variable length, ranging from one third to three quarters penis length. Epiphallic flagellum with small internal cryptae near epiphallus, tail of flagellum without visible cryptae. Spermatophore with smooth capsule; one complex branching spine on tail-pipe near capsule; opposite, eight increasingly smaller and simpler short branching spines spiraling around tail-pipe only (Fig. 10).
Remarks. This species was considered to be a synonym of Nitor circumcinctus for some years (Cox, 1909; Iredale, 1937a). Subsequently, its type locality was treated as doubtful and it was placed in incertae sedis (Iredale, 1941; Smith, 1992; Smith et al., 2002). After examination of the holotype the species was resurrected by Hyman (2007) with Expocystis exclusus as a synonym; this treatment is followed here.
Brevisentis jacksoniensis is found from Kiama to the Hawkesbury Valley in dry vine thicket, sclerophyll forest and woodland, living in litter and under logs and rocks (Fig. 11). It was recorded by Hyman and Ponder (2010) as ranging to the Warrumbungle National Park in the north, and in the west to Bathurst and the Blue Mountains, but this appears to be in error: specimens from all three localities have been identified herein as belonging to B. atratus. Specimens from Mulgoa and Richmond (W of Sydney), Palm Beach and Hornsby (N Sydney), Berowra Waters and Berowra Creek (N of Sydney) and Kurrajong (Hawkesbury Valley) have all been confirmed by sequencing or dissection to belong to B. jacksoniensis.
Fig. 11. Occurrence records of Brevisentis from the malacological collection of the Australian Museum, Sydney. Symbols: ● = B. jacksoniensis, Δ = B. atratus, + = B. kaputarensis , ♠ = B. n. sp. Wollemi NP.
While the three Brevisentis species all have very similar shells, the shell of B. jacksoniensis is slightly larger than B. kaputarensis, with more impressed sutures, and B. jacksoniensis has a higher spire than either of its congeners (Fig. 1A). This species can also be identified by its paler body colouration stained with red mucus. Brevisentis atratus also produces red mucus, but its black body colour renders it less visible. Anatomically, the species are easily distinguished by the longer penis with a blind tip seen in B. atratus and the absence of pustules in the penis interior of B. kaputarensis.