132 ST. FE. [cwap. vit, 
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 recent 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 nowis. As the 
remains of these genera are found on both sides of Behring’s 
Straitst 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 hollow- 
horned 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 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. 
+ See the admirable Appendix by Dr. Buckland to Beechey’s Voyage , 
also the writings of Chamisso in Kotzebue’s Voyage. 
