GASTEROPODA. 
CYCLOPHORUS (see p. 308). 
Sub-genera :—Jerdonia, Blanford, 1861. 
Type, J. trochlea, Benson sp. Nilgiri Hills, India. | 
Shell minute, umbilicated, pyramidal, horny, tricarinated ; 
operculum concentric, arctispiral, with a marginal sulcus all 
round; membranous internally, shelly externally; mner edge 
of each whorl resting on the outer edge of the next, 
Cyathopoma, Blanford, 1864. 
Type, OC. filocinctum, Benson sp. 
Shell minute, umbilicated, turbinated, or somewhat depressed ; 
epidermis thick, sometimes hispid, smooth, spirally striated, 
or lirated ; operculum truncate, conoid, concentric, multispiral ; 
internally membranous, externally shelly; external margins 
of the whorls raised in the form of shelly plates, incurved ; 
sometimes sculptured. 
Animal white, with a short oval foot, undivided beneath; 
tentacles small, black, with eyes at the base. 
Distribution, 5 species. India. 
SPIRACULUM, Pearson. 
Distinguished by the possession of a retroverted sutural tube 
epen at both ends, and by a modification of the form of the 
mantle corresponding to the same. 
Opisthoporus forms a sub-genus to Spiraculum. 
CLOSTOPHIS, Benson, 1860. 
Hiymology, clostos, coiled, and ophis, a serpent. 
Type, C. Sankeyi, Benson. Moulmein, Burmah. 
Shell subconic; penultimate whorl the largest, last whorl 
separate and descending, subaxial small ; aperture subcircular, 
entire, toothed; margin expanded. 
RHIOSTOMA, Benson, 1860. 
Etymology, rhion, a promontory. 
Type, R. Haughtoni, Benson. 
Shell subdiscoidal, broadly umbilicated ; last whorl separate, 
laterally descending ; aperture free, with an incision at the top, 
and a subtubular prominence crowning the slit; operculum 
toultispiral. 
Distribution, 6 species. Burmah, Siam, Cochin China. 
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