88 ON THE GEOGRAPHY OF ANIMALS. 
derive the singular Purpura 
Concholepas Sw. (fig. 37.) 
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 fiuviatile 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 Jvidina appears to be to Africa; while 
the Lymnadia gigas 
Sw. (fig. 58.) 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. hemastomus) 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 : — 
