(Figs. 1 A–C)

Material examined. – Holotype – 1 ex. (MZB.Gst.14.232), arboreal on low lying bushes and trees along a stream in damp forest just above sea level, about 1.2 km from the coast, Langgaliru (9°45'44"S 119°38'33"E), Southwest Sumba, Indonesia, coll. John Abbas, Sep.2007.

Paratypes.– 10 ex. (MZB.Gst.14.233); 5 ex. (ZRC.MOL.2832–2836), 1 ex. (ZRC.MOL.2960); 8 ex. (CSY409.003 amph048.00/01–08); 2 ex. (MNHN); 3 ex. (BMNH20080623) – same data as holotype.

Description. – Shell thin, sinistral, smooth with somewhat silky lustre; shell height up to 41.3 mm, width to 16 mm, aperture height to 21.2 mm in examined specimens; sinistral and slender ovately conical, covered with a thin periderm; whorls (6.5–7) rather flat, giving the shell a generally straight sided profile; outer lip thin and slightly expanded outwardly but not reflected; columella white, thin, slightly curved, without folds; umbilicus perforated or nearly closed; aperture large, about half of shell height, oblique, peristome basally rounded (“tear-drop” shaped); tip of apex faintly pinkishbrown, some individuals with a brown-black spot; parietal wall thin and transparent; ground colour light yellow or light to dark brown, decorated with variegated radial streaks or flames in the antepenultimate and penultimate whorls and an alternately blotched (somewhat checkered) subsutural spiral band; colour in aperture light yellow to brown.

Distribution. – Known thus far only from the type locality, probably endemic.

Etymology. – This species is named after Mr. John Abbas who collected, and kindly donated the specimens for our study.

Remarks. – No distinct dark axial bands marking interruptions in shell development (resting stage or varix) were observed in all examined specimens of Amphidromus (Syndromus) abbasi, new species. The alternately blotched subsutural band appears most prominently on the last whorl just above the periphery. The radial bands and patterns are consistent in most specimens examined, but are faintly marked or relatively monotonous in some. According to Laidlaw & Solem (1961), only Amphidromus (Syndromus) latestrigatus Schepman, 1892, and Amphidromus (Syndromus) floresianus Fulton, 1897 are known from Sumba Island. However, in terms of external morphology, Amphidromus (Syndromus) contrarius (Müller, 1774) (Fig. 1, D), and Amphidromus (Syndromus) filozonatus von Martens, 1867 (Fig. 1E) resemble Amphidromus (Syndromus) abbasi, new species, more. Some individuals of Amphidromus (Syndromus) abbasi, new species, with a light yellow ground colour may resemble similarly coloured Amphidromus (Syndromus) contrarius (Müller, 1774), while light brown forms are reminiscent of Amphidromus (Syndromus) filozonatus von Martens, 1867. Despite the suggested similarities with these congeners, the profile and peculiar teardrop-shaped aperture of Amphidromus (Syndromus) abbasi, new species, easily distinguishes it from other known Amphidromus (Syndromus) species.