168 ST. FE. 



splitting up of one gTcat region into two well- 

 characterized zoological provinces. The geologist, 

 who is fully impressed with the vast o,scillations of 

 level which have aftected the earth's crust within 

 late periods, will not fear to speculate on the re- 

 cent 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 Ameiican character of the 

 West Indian mammals* seems to indicate that this 

 archipelago was formerly united to the southern 

 continent, and that it has subsequently been an 

 area of subsidence. 



When America, and especially North America, 

 possessed its elephants, mastodons, horse, and hol- 

 low-hoi-ned ruminants, it was much more closely 

 related in its zoological characters to the temper- 

 ate parts of Europe and Asia than it now is. As 

 the remains of these genera ai'e found on both sides 

 of Behring's Straitsf and on the plains of Siberia, 

 we are led to look to the north-western side of 

 North America as the former point of communica- 

 tion between the Old and so-called New World. 

 And as so many species, both living and extinct, 

 of these same genera inhabit and have inhabited 

 the Old World, it seems most probable that the 

 North American elephants, mastodons, horse, and 

 hollow-horned ruminants migrated, on land since 

 submerged near Behring's Straits, from Siberia 

 into North America, and thence, on land since sub- 



* 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 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. 



t See the admirable Appendix by Dr. Bnckland to Beechey's 

 Voyage ; also the writings of Chamisso in Kotzebue's Voyage. 



