142 



of its body is covered by a somewhat firm cartilaginous, 

 straight, and transparent shell, like an inverted pyra- 

 mid, or in the form of a spear truncated and open at the 

 upper part; of a distinct shape in different species, and 

 not opened laterally, or at the posterior extremity, as 

 in the G. Hyalaea. 



Cleodora pyramidata Cleodora caudata. 



clio helicina. — Linn. 

 Shell thin, fragile, and papyraceous, its whorls spi- 

 ral and united in a discoid form, giving it a strong re- 

 semblance to the G. Helix; but in consequence of 

 the very wide umbilicus, formed by the position of 

 its whorls, it more nearly approximates the G< Planor- 

 bis. The animal of this shell has the power of re- 

 ceding altogether within its covering, in which it dif- 

 fers from the preceding genus. Lamarck considers the 

 name of Limacina less applicable to this genus than 

 that of Helicina, given to it by Gmelin. 

 Limacina helicialis. 



