140 MANUAL OF THE MOLLUSCA. 



Type, A. australis, PL IX., fig. 33. 



Shell globular, with an uneven, battered, surface ; columella fissured ; 

 outer lip channelled near the suture ; operc. horny, sub-spiral. Animal with- 

 out tentacles ; eyes placed on round lobes ; air-breathing ; respiratory cavity 

 closed, except a small valvular opening on the right side ; a large gland occu- 

 pies the position of the gill of paludina ; sexes united (Quoy). Mr. Gray 

 places this genus amongst the true pulmonifera. 



Distr., 3 sp. Shores of New Zealand and the Pacific Islands. The living 

 shells sometimes have serpula attached to them (Cuming). They are eaten 

 by the New Zealanders. 



VALVATA, Miiller. Valve-shell. 



Types, V. piscinalis, PI. IX., fig. 28. V. cristata, PI. IX., fig. 29. 



Shell turbinated, or discoidal, umbilicated ; whirls round or keeled ; aper- 

 ture not modified by the last whirl ; peristome entire ; operc. horny, multi- 

 spiral. 



Animal with a produced muzzle ; tentacles long and slender, eyes at their 

 outer bases ; foot bi-lobed in front ; branchial plume long, pectinated, parti- 

 ally exserted on the right side, when the animal is walking. Lingual teeth 

 broad ; uncini 3, lanceolate ; all hooked and denticulated. 



Dislr., 6 sp. Brit., N. America. 



Fossil, 19 sp. Wealden . Brit., Belgium, &c. 



FAMILY VIII. NERITIDJS. 



Shell thick, semi-globose; spire very small; cavity simple, from the 

 absorption of the internal portions of the whirls ; aperture semi-lunate ; colu- 

 mellar side expanded and flattened ; outer lip acute. Operculum shelly, sub- 

 spiral, articulated. 



At each end of the columella there is an oblong muscular impression, 

 connected on the outer side by a ridge, on which the operculum rests ; within 

 this ridge the inner layers of the shell are absorbed. 



Animal with a broad, short muzzle, and long slender tentacles ; eyes on 

 prominent pedicels, at the outer bases of the tentacles ; foot oblong, triangular. 

 Lingual dentition similar to the turbinidce. Teeth 7 ; uncini very numerous. 



Fig. 85.* 

 * Fig. 85. Nerita polita, L. (from Quoy and Gaimard) New Ireland. 



