Paraboysidia serpa

Shell relatively small, with a conical spire issuing from a rather broad base. The wide aperture is not disjunct, but adnate to the preceding whorl. Shell is reddish-brown and opaque. First 1.5 whorls lack ornamentation, progressing into weakly striated and ribbed subsequent ultimate whorls. Last whorl (of 5) ends straight or partially descending. Whorl peripheries rounded except for a conspicuous peripheral keel on the ultimate whorl, with a similar keel encircling the umbilicus. Umbilicus rather wide and open. Aperture wide, with separated angular and parietal lamellae; columella, upper and lower palatal teeth large, infraparietal, basal and interpalatal teeth small. Peristome continuous, thickened and expanded. Height: 2.9-3.4 mm, Breadth: 2.6-3.1 mm, Apertural height: 1.4-1.6 mm [among type series and references of Benthem-Jutting, 1949]. P. serpa resembles Gyliotrachela modesta in general form, but the latter differs in its disjunct ultimate whorl and lesser-developed apertural armature.[2]

Paraboysidia serpa is endemic to the limestone karst of Bukit Baling, Kedah, Malaysia. It occurs among lowland dipterocarp woodlands which are threatened by desiccation (which has been tied to population declines in karst-endemic fauna), and possibly pollution from quarrying operations or changing forest structure. Due to the extremely narrow and imperiled endemic site of this species, it has been declared Critically Endangered by the IUCN under criteria B1ab(i,iii)+2ab(i,iii).