J 4 ZONITID^J. 



Genus CIIAROPA, Albers, 1860. 



Shell umbilicated, depressed, ribbed, usually hairy ; periphery 

 rounded. 



Animal with caudal mucous gland. Jaw flat-ribbed. Mar- 

 ginal teeth of the radula broad, usually with many points. 



New Zealand, Polynesia. 



Button (Trans. N. Zeal. Inst., xvi, 200) has made this the 

 type of a family Charopidse, the animal having heliciform den- 

 tition, with a mucus-gland on the tail, as in Zonites. 



Section CHAROPA (typical). 



Section GERONTIA, Button, 1884. 



Shell depressed, widely umbilicated, striated ; periphery 

 rounded ; whorls about five, slowly increasing ; aperture oblique. 



Animal heliciform ; mantle rather posterior, included ; tail 

 acute, with a mucus-pore but no papilla ; jaw smooth or striated. 



New Zealand. 



Section PYRBHA, Button, 1884. 



Shell subperforate, thin, translucent, of 4^-5^- regularly in- 

 creasing whorls. Mantle subcentral, reflected over the peris- 

 tome of the shell with an even margin; tail truncate, with a 

 large papilla and mucous gland. Jaw with flat ribs. Marginal 

 teeth broad, with several points. New Zealand. 



Section PSYRA, Button, 1884. 



Imperforate or narrowly umbilicated, ribbed, not hairy, 

 periphery rounded. Jaw and teeth as in Charopa. 



New Zealand. 



Section THERASIA, Button, 1884. 



Subperforate or narrowly perforate, conoidal, depressed, 

 periphery subearinated ; whorls smooth, striated or with mem- 

 branous plaits. Jaw with flat ribs. Marginal teeth broad, 

 usually with several points. New Zealand. 



Section THALASSTA, Albers, 1860. 



Shell narrowly or moderate^ perforate, conic orbicular, thin, 

 pellucid ; whorls five or six, smooth or with membranous plaits, 

 slowly increasing, the last round or with angulate or carinate 

 periphery ; umbilical region impressed ; peristome simple, acute, 

 columellar margin slightly reflexed. Jaw flat-ribbed. Marginal 

 teeth longer than broad, witli one point very much longer than 

 the others. New Zealand, Australia, Polynesia. 



