Discartemon stenostomus Benthem Jutting, 1954

Siriboon, Thanit, Sutcharit, Chirasak, Naggs, Fred, Rowson, Ben & Panha, Somsak, 2014, Revision of the carnivorous snail genus Discartemon Pfeiffer, 1856, with description of twelve new species (Pulmonata, Streptaxidae), ZooKeys 401, pp. 45-107 : 78

21. Discartemon stenostomus Benthem Jutting, 1954 Figs 9A, B, 23

Discartemon stenostomus - Benthem Jutting 1954: 83, 86, fig. 5. Type locality: Kaki Bukit, Perlis, Malaysia. Benthem Jutting 1959: 168. Berry 1965: 221-228, figs 1-3. Richardson 1988: 184. Maassen 2001: 88. Maassen 2003: 119. Marwoto 2008: 192.

Material examined.

Holotype ZMA 3.54.024 (Fig. 9A). Paratypes ZMA 3.54.025 (8 shells), and NHMUK 1957-4-3.1-2 (2 shells). Kaki Bukit, Perlis: NMW 1955.158.25256 (10 shells).

Remarks.

Shell globose-heliciform, semi-transparent, spire only slightly convex and with a distinct suture. Shell surface glossy with thin transverse ridges at suture; following whorls regularly coiled. Last whorl rounded and regularly expanded; umbilicus widely open and deep. Aperture triangular; peristome thickened, expanded and reflected. Apertural dentition with one sinuous parietal, one palatal, one columellar and one supracolumellar lamella (Fig. 9A).

The genital anatomy was described by Berry (1965). Atrium and penis short with blunt penial appendix, penial sheath extending almost entire penis length, vas deferens passing through about one-fifth of penial sheath length. Internal wall of penis corrugated with cornified ridges, penial hooks absent, but with a large hollow “stylet” presumably protrudable from the tip of the everted penis. Vagina very short, proximal gametolytic duct enlarged, distally a long slender tube. Free oviduct short; talon small, club shaped; seminal vesicle about the same length from talon to branching point of seminal vesicle. Internal wall of vaginal elaborated with parallel vaginal folds.

This species resembles Discartemon lemyrei and Discartemon collingei , but differs in having thin transverse ridges near the suture, a triangular aperture, and apertural dentition with a sinuous parietal lamella, one palatal, one columellar and one supracolumellar lamella. In addition, Discartemon lemyrei has a larger shell, narrower umbilicus, and only one parietal lamella, while Discartemon collingei has a shouldered and slightly axially reflected last whorl, and apertural dentition with a straight parietal, one palatal, one basal and one columellar lamellae. A penial stylet has not yet been found in any other Discartemon species.