124 ST. F. [CHAP. vir. 



with the exception of some valleys and of a fringe of low land on 

 the coast, a broad barrier ; we shall then have the two zoological 

 provinces of North and South 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 charac- 

 terized 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 pecu- 

 liar 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 zoolo- 

 gical 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 eleva- 

 tion 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 * 



* See Dr. Richardson's Report, p. 157 ; also L'Institut, 1837, p. 253. 

 Cuvier says the kinkajou is found in the larger Antilles, but this is doubt- 

 ful. M. Gervais states that Ihe Didelphis crancrivora is found there. It 

 is certain that the AVest Indies possess some mammifers peculiar to them- 

 selves. A. tooth of a mastodon has been brought from Bahama : Ediii. 

 New Phil. Journ., 1826, p. 395. 



