1833. J ZOOLOGY OF NORTH AND SOUTH ATuEKICA. 131 



ruminant, discovered by MM. Lund and Clausen in the caves of 

 Brazil, are highly interesting facts with respect to the geo- 

 graphical distribution of animals. At the present time, if we 

 divide America, not by the Isthmus of Panama, but by the 

 southern part of Mexico* in lat. 20^, where the great table-land 

 presents an obstacle to the migration of species, by affecting the 

 climate, and by forming, 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 Korth and South 

 America strongly contrasted with each other. Some few species 

 alone have passed the barrier, and may be considered as wander- 

 ers from the south, such as the puma, opossum, kinkajou, and pec- 

 cari. 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 in- 

 cludes 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 ele- 

 phant, mastodon, horse, and three genera of Edentata, namely, 

 the Megatherium, Megalonyx, and Mylodon. ^Within nearly this 

 same periods (as proved by the shells at Bahia Blanca) South 

 America possessed, as we ha%e 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 q-enera in common, were much more closelv related 

 in the character of their terrestrial inhabitants than they now are. 



* This is the geographical division followed by Liclitenstein, Swaiiison, 

 Eiichson. and Richardson. The section from Vera Cruz to Acapulco, given 

 by Humboldt in the Polit. Essay on Kingdom of N. Spain, will show how 

 immense a barrier the iNIexican table-land forms. Dr. Richardson, in his 

 admirable Report on the Zoology of N. America read before the Brit. Assoc. 

 1836 (p. 157), talking of the identification of a Mexican animal with the 

 Si/netheres preliensilis, S'dys, "We do not know v. ith what propriety, but if 

 correct, it is, if not a solitary instance, at least very nearly so, of a rodent 

 animal being common to North and South America.' 



