Gastroptychia geoffreyi Chen & Ablett, 2024, sp. nov.

Gastroptychia geoffreyi sp. nov. (Figure 2) Diplommatina n. sp. (sinistral) Nevill, 1878: 287. Diplommatina n. sp. (prox. D. costulata, Hut.) Nevill, 1878: 287. Type specimens. Holotype: NHMUK 20240334/1, label: 34. Diplommatina n. sp. (sinistral), 10. Darjeeling, Dr F. Stoliczka; 35. Diplommatina n. sp. 2. Darjeeling, n. sp. [current geopolitical location: Darjeeling, West Bengal, India]. ex. Indian Museum Collection. Paratypes: NHMUK 20240334/2-10 (9 specimens), same data as holotype. Etymology. This new species is named after Geoffrey Nevill (1843–1885), who first recognised this species as new to science. Diagnosis. Gastroptychia geoffreyi sp. nov. is characterized by the ovately fusiform shell, with convex body whorl, dense ribs on the teleoconch surface and a columellar tooth weakly emerged from aperture. Description. Shell small, sinistral, light brown, ovately fusiform, with4.5–4.75 convex whorls; suture impressed; apex blunt; body whorl at same width as penultimate whorl. Protoconch consisting of 1.25–1.5 whorls, somewhat matte; boundary between protoconch and teleoconch clear. Teleoconch surface with fine and regularly arranged radial and prosocline ribs, approximately 7 ribs per 500 μm on the body whorl, very weak and dense spiral threads situated, distinct on the body whorl. Aperture oval, slightly oblique to the shell axis. Peristome double, spaced, attached to the body whorl; callus thin or slightly thickened; outer peristome expanded, at the same height as inner peristome; inner peristome expanded but not reflected, central part of the palatal margin slightly to significantly curved inward. Internal constriction presents ventrally with a thin basal radial (to the shell axis) palatal fold. Other internal structure unknown, no horizontal palatal lamella observed through translucent shell. Columellar tooth weakly emerged from aperture. Umbilicus closed. Operculum unknown. Measurements. Shell height: 2.48–2.53 mm, shell width: 1.46–1.50 mm, aperture height: 0.98–1.03 mm, aperture width: 1.01–1.06 mm (n = 2). Differential diagnosis. The new species, from the foothills of the eastern Himalayas, is distinct from species from the Shillong Plateau, i.e. Gastroptychia collicola sp. nov., Gastroptychia gibberosa (Godwin-Austen, 1892), Gastroptychia gibbosa (W. T. Blanford, 1868) and Gastroptychia jaintiaca (Godwin-Austen, 1870), by the dense ribs on the surface of the shell, lateral side of the body whorl very convex in aperture view and the small columellar tooth. Gastroptychia geoffreyi sp. nov. also somewhat resembles Diplommatina sulcicollis Möllendorff, 1897 and Diplommatina javana Möllendorff, 1897 from Java and Bali in general shape, and both of which also have small columellar tooth present (Nurinsiyah & Hausdorf 2017, Vermeulen & Whitten, 1998). The new species differs from latters by its spaced double peristomes and relatively strong ribs. Distribution. INDIA: West Bengal. The new species is known only from the type locality.