GASTEROPODA. 183 



Animal with a squarish, disk-like head, eyes sessile in the centre ; mantle not 

 investing; a posterior lobe; lateral lobes enveloping. (Pl.XIV. lig. 8, not 7) 



ACERA, Miiller. 



Type, A. bullata, Pi. XIV. fig. 9. Etym. Akeros, hornless. 



Shell thin, flexible, globosely* cylindrical, spire truncated, whirls chan- 

 nelled ; aperture long, expanded and deeply sinuated in front, outer margin 

 disunited at the suture ; columella open, exposing the whirls. 



Animal with a short and simple head-lobe, truncated in front and eyeless ; 

 lateral lobes nearly concealing the shell ; lingual teeth hooked and serrulate, 

 laterals about 40, narrow, claw-shaped ; gizzard armed with horny teeth. 



Distr. 7 sp. Greenland, Brit. Medit. Zanzibar, India, New Zealand. 



A. bullata is found amongst weed, in 1 15 fms. water (Forbes). 



CYLICHNA, Loven. 



Type, C. cylindracea, PL XIV. fig. 10. Syn. Bullina, Risso. 



Shell strong, cylindrical, smooth or punctate- str iate ; spire minute or 

 truncated ; aperture narrow, rounded in front ; columella callous, with one 

 plait. 



Animal short and broad, not investing the shell ; head flattened, truncated 

 in front, with sub -centrally immersed eyes, tentacular lobes more or less 

 united ; foot oblong, posterior and lateral lobes not much developed ; gizzard 

 armed; lingual teeth squarish, recurved and serrated, with 1 large and 5 or 

 6 small hooked laterals. 



Distr. 20 sp. U. States, Greenland, Brit. Red Sea, Australia. 



Fossil. Miocene . Brit. 



