Stomacosmethis Bollinger, 1918

Pall-Gergely, Barna, Sajan, Sheikh, Tripathy, Basudev, Meng, Kaibaryer, Asami, Takahiro & Ablett, Jonathan D., 2020, Genus-level revision of the Alycaeidae (Gastropoda, Cyclophoroidea), with an annotated species catalogue, ZooKeys 981, pp. 1-220 : 1

Genus Stomacosmethis Bollinger, 1918

Alycaeus (Stomacosmethis) Bollinger, 1918: 316.

Alycaeus (Stomacosmethis) - Egorov 2013: 34.

Type species.

Alycaeus (Stomacosmethis) sarasinorum Bollinger, 1918 (Fig. 39C ), SD Egorov (2013: 34).

Diagnosis.

Shell small to very large (D: 3-13 mm), usually brightly coloured yellow or orange; shell shape triangular or depressed triangular; protoconch smooth without spiral striation; R1 usually finely reticulated, without prominent ribs; R2 very short, usually roughly, weakly wrinkled, R3 long, with blunt swelling. Operculum thin, outer surface smooth or with outer, elevated, trumpet-like projection. The outer operculum surface can also be finely granulated, flaky or have short calcareous spikes ( Foon and Liew 2017). Central radular tooth elongated, usually with a single central cusp only, or central cusps with one or two small cusp at each side.

Differential diagnosis.

Most species classified in this genus were previously described in Alycaeus . However, Alycaeus species are characterised by a very long R2, whereas the R2 is extremely short is Stomacosmethis . Pincerna species possess a globular shell with more widely spaced ribs, and they are usually not colourful. The distinction of Stomacosmethis and Pincerna requires further examination. See also under Pincerna (p. 147).

Distribution.

This genus is distributed in the tropical forests of the Malay Archipelago (Malay Peninsula, Borneo, Java, Sumatra, Sulawesi).

Remarks.

This genus was originally diagnosed based on the calcareous, pipe, tongue or cup-shaped structure on the outer side of the operculum. Since the circular opercular structures have evolved multiple times, this genus must be re-diagnosed. The type species belongs to a clearly delineable group of the Alycaeidae having triangular, colourful shells, dense, fine ribs and short tube, which is now called Stomacosmethis . See also under S. balingensis , which is exceptional in terms of shell shape.

Figures

Figure 39. Type species of alycaeid genus-group taxa A Pincerna constricta (Benson, 1851), syntype (NHMUK 1906.4.4.41; type species of Cycloryx) B Pincerna liratula (Preston, 1907), syntype (NHMUK 1907.5.20.191; type species of Pincerna) C Stomacosmethis sarasinorum (Bollinger, 1918), lectotype (NHMB 2411. a; type species of Stomacosmethis). Photographs: Harold Taylor (A, B); Eduard Stoeckli (C).