COLIMACEA. 173 



adopted, subservient both to memory and convenience, lias 

 divided the Collmacea into nine genera, distinguisliing the 

 Auriculacea and Cyclostomacea as separate families. The 

 former differ in being partially aquatic, and in their shells 

 being always strongly plaited at the columella ; the latter 

 are terrestrial, their shells are distinguished by the rotundity 

 of the aperture, and in being uniformly operculated. 



The geographical distribution of this interesting family 

 is a subject of no small interest in connection with that of 

 mollusks in general. Climate has, doubtless, a decided 

 influence in this respect ; but, as a greater uniformity of 

 temperature prevails in the waters of the ocean than on 

 land, the diffusion of marine mollusks is more extensive. 

 As yet, no means have been discovered whereby to ascertain 

 the submarine provinces of shells, as those of terrestrial 

 and even subaqeous plants, although no doubt exists that 

 the boundaries both of latitude and longitude, with regard 

 to oceanic shells, are in general well defined. 



The following are nine genera into which the family 

 Colimacea are divided : — Helix, Carocolla, Anasfoma, Pupa, 

 Clausilia, Bidimiis, PaHida, Achatina, and Succinea. 



Paley justly observes, that a snail-shell is a wonderful, a 

 mechanical, and, if we may so express ourselves concerning 



