132 ST. Ffi. [CHAP. TII. 



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 probably, on the iccent submergence of land in the West 

 Indian Archipelago, as the cause of the present zoological sepa- 

 ration of North and South America. The South American 

 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 hollow-horned ruminants, it was 

 much more closely related in its zoological characters to the 

 temperate parts of Europe and Asia than it now is. As the 

 remains of these genera are 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 

 communication 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 hollovv- 

 liorned ruminants migrated, on land since submerged near Beh- 

 ring's Straits, from Siberia into North America, and thence, on 

 land since submerged in the West Indies, into South America, 

 where for a time they mingled with the forms characteristic of 

 that southern continent, and have since become extinct. 



While travelling through the country, I received several vivid 

 descriptions of the effects of a late great drought ; and the 

 account of this may throw some light on the cases where vast 



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

 Cuvier gays 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. Jouru. 

 1826, p. 395. 



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

 also the writings of Chamisso in Kotzebue's Voyage. 



