GASTEUOPODA. 305 



Shell obtusely cone-sliaped, smooth ; spire short, flat-whorlod ; 

 aperture long, narrow; lip sharp, denticulated within; colu- 

 mella twisted in front ; wall of the apertui*e with 1 or 2 spiral 

 plaits. 



Animal vdih. short, tapering, and rather compressed tentacles ; 

 foot divided transyersely into two portions, advanced successively 

 in walking. 



Distrihution, 56 species. "West Indies, Europe. In salt- 

 marshes and on the sea- shore. The British species have thin 

 ovate shells, with the spire moderatelj'' produced, and the aper- 

 ture oval. They form the sub-genus Alexia (denticulata), 

 Leach. 



Fossil, Eocene. Britain, France. 



Cahychitjm, MiiUer 



T7/pe, C. minimum, PI. XII., Eig. 39. 



Synonym, Auricella, Hartm. 



Bhell minute, oblong, finely striated transversely; aperture 

 oval, toothed, margin thickened, united by callus. 



Animal, with 2 blunt, cylindrical tentacles ; eyes black, 

 sessile, near together, behind the tentacles. 



Distrihution, 9 species. Europe; North America. At tha 

 roots of grass in damp places, especially near the sea. 



Fossil, 3 species. Miocene — . Europe. 



The genus Siphonaria, described at p. 281, is supposed to be 

 pulmoniferous, and to bear somewhat the same relation to 

 Auricula that Ancylus docs to Limnaea. The lingual dentition 

 is similar to Auricula ; the centre teeth are distinct, the laterals 

 numerous and hooked. 



Fig. 133.» 



Section B. — OPERCTJLATA.f 

 The Operculated land-snails are exceedingly like periwinkles 



* Siphonaria species from the Cape ; three rows of teeth, c central, / laterals, from 2 

 preparation by J. W. Wilton, Esq., of Gloucester. 



t Phanera-pneiimona (open-lunged), Gray. The account of this group ia chiefiy 

 Uiken from the catalogue prepared by my friend Dr. Baird. 



