344 TROPICAL NATURE, AND OTHER ESSAYS. 



tropical climate, while even tlie extreme north would 

 support a luxuriant vegetation. This great continent 

 would abound in animal life, and would be especially 

 remarkable for its mammalia, which would comprise 

 ancestral forms of all our existing higher types, along 

 with a number of those lower grades of organisation 

 (such as lemurs and opossums) now found chiefly in the 

 southern hemisphere. 



Connected with this continent by what is now 

 Behring Straits and the Sea of Kamschatka, we should 

 find North America, perhaps somewhat diminished in 

 the east, but more extensive in the south and north, and 

 abounding as now with great inland lakes which were 

 situated to the west of the present lake district. This 

 continent seems to have had a less tropical climate and 

 vegetation than prevailed in the eastern hemisphere, but 

 it supported an almost equally varied though very 

 distinct fauna. Ancestral horses no larger than dogs ; 

 huge tapir-like and pig-like animals ; strange forms allied 

 to rhinoceroses ; the Dinocerata huge horned animals 

 allied to elephants and to generalised Ungulata; and 

 the Tillodontia, still more unlike anything now living, 

 since they combined characters now found separated in 

 the carnivora, the Ungulata, and the rodents. Ancestral 

 Primates, allied to both the lemurs and the South 

 American monkeys, also inhabited this continent. 



The great land masses of the northern hemisphere 

 thus appear to have possessed between them all the 

 higher types of animal life ; and these seem to have 

 been developed for a time in one continent and then to 

 have been in part transferred by migration to the other, 

 where alone they have sometimes maintained themselves. 



