Stomacosmethis cf. jagori (E. von Martens, 1860)

Figs 5 a, 9 b

Alycaeus jagori E. von Martens, 1860: 208.

Stomacosmethis jagori – Páll-Gergely et al. 2020: 191.

Material examined.

Indonesia • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 10); 4°04.11'S, 103°55.34'E; alt. 158 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24141/78 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 11); 4°04.11'S, 103°55.34'E; alt. 124 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24138/450 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 8); 4°04.06'S, 103°55.40'E; alt. 134 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24128/78 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 16); 4°04.34'S, 103°56.06'E; alt. 139 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24129/10 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 2); 4°04.00'S, 103°55.79'E; alt. 158 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24125/11 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 4); 4°04.01'S, 103°55.89'E; alt. 111 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24126/7 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 7); 4°04.06'S, 103°55.52'E; alt. 126 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24123/26 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 5); 4°04.04'S, 103°55.36'E; alt. 150 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24124/3, MZB Gst. 24139/23 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 13); 4°04.24'S, 103°55.70'E; alt. 170 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24122/16 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 3) 4°04.23'S, 103°56.08'E; alt. 114 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24151/5 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 12); 4°04.16'S, 103°55.46'E; alt. 154 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24149/2, MZB Gst. 24127/12 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Suka Merindu (Plot 9); 4°04.09'S, 103°55.36'E; alt. 122 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24142/1 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 15); 4°04.33'S, 103°55.60'E; alt. 205 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24150/1 • South Sumatra, Ogan Komering Ulu, Semidang Aji, Padang Bindu (Plot 14); 4°04.24'S, 103°55.75'E; alt. 154 m; May-June 2021; A. S. Nurinsiyah leg.; MZB Gst. 24140/27.

Description (n = 98).

Shell small size with H = 6.1–11.6 mm (mean 8.8 mm); D = 7.7–12.6 mm (mean 9.2 mm); HA = 3.4–5.6 mm (mean 4.2 mm); DA = 3.6–5.6 mm (mean 4.3 mm); 5–6 whorls; operculum height 2.7–3.6 mm, operculum width 2.6–3 mm. operculum concavity / thickness 0.61–0.78 mm. Shell dextral; conical shaped, with depressed apex; pale lime yellow to white, sub-transparent, the spire (protoconch) darker than the last whorl, smooth; teleoconch with fine and close radial ribs; spiral striae present; last whorl very large; constriction ~ 2–3 mm from the aperture; a small breathing tube (sutural tube) present; micro-tunnel under sutural tube; aperture almost perfectly round, slightly oblique at the top; peristome continuous, thick, and double; umbilicus open very small; operculum round, with concave rounded surface, convex inner surface, multispiral with central nucleus.

Habitat.

Limestone rocks.

Distribution.

The specimens collected in Sumatra are provisionally identified as Stomacosmethis jagori (see Remarks). The distribution in South Sumatra is a new record.

Remarks.

The genus Stomacosmethis has not been revised yet, and it is considered challenging, because the shell characters are relatively few. Namely, with a few exceptions, the shell shape and sculpture are relatively uniform across the genus, and the sutural tube (the length of which is an important character in other genera of this subfamily) is always very short. Several new species described by Foon and Liew (2017) are treated as subspecies in a later review (Páll-Gergely et al. 2020). Currently, 26 species are considered valid (Páll-Gergely et al. 2020; MolluscaBase 2025). The specimens we found in Sumatra are most similar to Stomacosmethis jagori (Fig. 5 b), which was originally described from Java, and was subsequently reported from Sulawesi and Borneo (van Benthem Jutting 1948; Hendriks et al. 2019), although the identity of the populations from Borneo are questionable (Páll-Gergely et al. 2020).

We note, however, that shells of Stomacosmethis kelantanensis clementsi (Foon & Liew, 2017) (originally described as Alycaeus clementsi) from Peninsular Malaysia are also similar to our shells from Sumatra. However, they are probably not closely related due to the large geographic distance between them. Minor differences are observed between the Stomacosmethis kelantanensis clementsi shells and the ones we collected in both shell size and the sculpture of the radial ribs, with the Padang Bindu population displaying relatively larger shells and smoother radial ribs.