This paper described the second species of the genus Calybium Morlet, 1892, Calybium plicatus sp. nov. was collected in Son Doong Cave, Phong Nha–Ke Bang National Park, Quang Binh Province, Central Vietnam. Calybium plicatus sp. nov. has a similar shell shape to Calybium massiei Morlet, 1892 but differs in having a smaller shell size, the parietal wall with six evenly spaced parietal lamellae. This discovery represents the first report of the genus Calybium in Vietnam.

Class Gastropoda Cuvier, 1795

Subclass Neritimorpha Cox, 1960

Order Cycloneritida Frýda, 1998

Superfamily Helicinoidea Férussac, 1822

Family Helicinidae Férussac, 1822

Subfamily Vianinae Baker, 1922

Calybium Morlet, 1892

 

Diagnosis. Shell medium-sized, depressed coni-cal, and sharply keeled body whorl; the calcareous layer on the dorsal side is coarse, strongly undulated and forms evenly spaced domes protruding from the shell surface; parietal wall with six lamellae, of which the sixth very long, curved, and close to the suture; palatal wall with a barrier-shaped lamella that ...

Etymology. The species’ name is derived from its characteristic apertural dentition, from the Latin word ‘plicatus’, meaning ‘lamellae’ that are present at the parietal wall.

 

Calybium plicatus sp. nov.  A, B. Habitat picture, from the type locality at Doline 1 of Son Doong Cave, Bo Trach District, Quang Binh Province. C. Photo of the new species in habitat. Photos: Vu V.L. (A, B), Hoang N.K. (C).