UNIVALVE MOLLUSC ANS. 291 



is impeded by a dry soil, and that the grains of 

 earth and small stones, when quite dry, adhere 

 to their slimy foot. 



As many of the marine shells appear in some 

 degree amphibious, for instance, the Chitons and 

 the Limpets, so, perhaps, some of the terrestrial 

 ones may occasionally enter fresh waters ; indeed 

 the amber shells, 1 at least one species, 2 is stated 

 to swim occasionally on the surface of the water. 

 From these circumstances it seems not im- 

 probable that the shell-fish, as well as the birds, 

 so vast a proportion of them being marine ani- 

 mals, were all amongst the objects created on the 

 fifth day, and produced by the waters. 



There are very large and beautiful shells 

 found in South America, belonging to the terres- 

 trial herbivorous section and to different genera 3 

 divided from Helix of Linne, but we know 

 nothing of their history or habits, I shall there- 

 fore now say something upon the marine herbi- 

 vorous Trachelipods. 



The violet snail, 4 which, according to the ac- 

 count of its manners given by Bosc, who paid 

 particular attention to them in a voyage from 

 France to America, exhibits several very re- 

 markable peculiarities. When the sea is calm, 

 these animals may be seen collected often in 



1 Succinea. 2 s. elongata. 



3 For instance, Achatina Bulimus, fyc. 



4 lanthina, PLATE VI. FIG. 2. 



