88 ON THE GEOGRAPHY OF ANIMALS. 



derive the singular Purpura 

 Concholepas Sw. (fig. SI .) 

 which resembles a limpet; 

 and also a considerable num- 

 ber of chitons. The marine 

 shells of Brazil are com- 

 paratively few, and offer a 

 singular contrast to the pro- 

 lific shores of intertropical 



India, and even to those of Western Africa. The num- 

 ber of fluviatile shells bears no comparison with those of 

 North America ; but whether this is truly the case in 

 nature,, or that it results from the rivers of the South 

 not having been sufficiently explored, is still uncertain. 

 The genus Hyria Lam. is as peculiar to these American 

 latitudes, as Iridina appears to be to Africa; while 



the Lymnadia gigas 

 Sw. (fig, 38.) of the 

 Oronoko is the most 

 gigantic river shell hi- 

 therto discovered. The 

 apple-snails (Ampul- 

 laria L.) abound in 

 the swamps and lesser 

 rivers, and exhibit nu- 

 merous species, none of 

 which appear to have been found north of the line. 



(124.) The land shells, although not many, are very 

 curious. The large Bulimus ovatus is common on the 

 continent ; while another species (B. hcemastomus} ap- 

 pears more frequent in the islands. The Achatina mela- 

 nastoma Swains, is particularly rare, and none of the 

 species from the continent of tropical America may be 

 termed common. Jamaica, and several of the neigh- 

 bouring islands, are much richer in these productions. 



(125.) The quadrupeds of the American continent 

 chiefly belong to the following genera and sub- 

 genera : 



