1833.] SPECIFIC ZOOLOGICAL ."DIVISIONS. 137 



great table-land presents an obstacle to\the migration of 

 species, by affecting the climate, and by irpnning, with the 

 exception of some valleys and of a fringe ^of low land on 

 the coast, a broad barrier ; we shall then ihaye the two 

 zoological provinces of North and South Ameirica 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 characterized 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 armadillos. North America, on the other hand, is 

 characterized (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 geological 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-characterized 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 prob- 

 ably, 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* seems 



" See Dr. Richardson's Report, p. icy; also L'lnstitut, 1837, p. sm. 

 ivier says the kinkajou is found in the Larger Antilles, but this is doubtful. 



