VII 
ZOOLOGY OF NORTH AND SOUTH AMERICA 
139 
America strongly contrasted with each other. Some few species 
alone have passed the barrier, and may be considered as 
wanderers from the south, such as the puma, opossum, kinkajou, 
and peccari. South America is characterised by possessing 
many peculiar gnawers, a family of monkeys, the llama, peccari, 
tapir, opossums, and, especially, several genera of Edentata, the 
order which includes the sloths, ant-eaters, and armadilloes. 
North America, on the other hand, is characterised (putting on 
one side a few wandering species) by numerous peculiar gnawers, 
and by four genera (the ox, sheep, goat, and antelope) of hollow¬ 
horned ruminants, of which great division South America is 
not known to possess a single species. Formerly, but within 
the period when most of the now existing shells were living, 
North America possessed, besides hollow-horned ruminants, the 
elephant, mastodon, horse, and three genera of Edentata, namely, 
the Megatherium, Megalonyx, and Mylodon. Within nearly 
this same period (as proved by the shells at Bahia Blanca) 
South America possessed, as we have just seen, a mastodon, 
horse, hollow-horned ruminant, and the same three genera (as 
well as several others) of the Edentata. Hence it is evident 
that North and South America, in having within a late geo¬ 
logical period these several genera in common, were much more 
closely related in the character of their terrestrial inhabitants 
than they now are. The more I reflect on this case, the more 
interesting it appears : I know of no other instance where we 
can almost mark the period and manner of the splitting up of 
one great region into two well-characterised zoological provinces. 
The geologist, who is fully impressed with the vast oscillations 
of level which have affected the earth’s crust within late periods, 
will not fear to speculate on the recent elevation of the Mexican 
platform, or, more probably, on the recent submergence of land 
in the West Indian Archipelago, as the cause of the present 
zoological separation of North and South America. The South 
American character of the West Indian mammals 1 seems to 
indicate that this archipelago was formerly united to the southern 
continent, and that it has subsequently been an area of subsidence. 
1 See Dr. Richardson’s Report , p. 157 ; also LTnstiiut, 1837, p. 253. Cuvier 
says the kinkajou is found in the larger Antilles, but this is doubtful. M. Gervais 
states that the Didelphis crancrivora is found there. It is certain that the West 
Indies possess some mammifers peculiar to themselves. A tooth of a mastodon has 
been brought from Bahama : Edin. New Phil. Journ. 1826, p. 395. 
