132 DISTRIBUTION OF EXTINCT ANIMALS. [part n. 



migration had occurred for countless preceding ages, proves that 

 some great barrier to the entrance of terrestrial mammalia 

 which had previously existed, must for a time have been re- 

 moved. We must defer further discussion of this subject till 

 we have examined the relations of the existing faunas of North 

 and South America. 



Tektiaey Period. 



When we get to remains of the Tertiary age, especially those 

 of the Miocene and Eocene epochs, we meet with so many 

 interesting and connected types, and such curious relations with 

 living forms in Europe, that it will be clearer to trace the 

 history of each order and family throughout the Tertiary period, 

 instead of considering each of the subdivisions of that period 

 separately. 



It will be well however first to note the few American Post- 

 Pliocene or living genera that are found in the Pliocene beds. 

 These consist of several species of Canis, from the size of a fox 

 to that of a large wolf; a Fclis as large as a tiger ; an Otter 

 (Lutra) ; several species of Hipparion ; a peccary (Dicotyles) ; 

 a deer (Cervus) ; several species of Procamelus ; a mastodon; 

 an elephant; and a beaver (Castor). It thus appears that out 

 of nearly forty genera found in the Post-Pliocene deposits, only 

 ten are found in the preceding Pliocene period. About twelve 

 additional genera, however, appear there, as we shall see in 

 going over the various orders. 



Primates. — Among the vast number of extinct mammalia 

 discovered in the Tertiary deposits of North America, no 

 example of this order had been recognized up to 1872, when 

 the discovery of more perfect remains showed, that a number 

 of small animals of obscure affinities from the Lower Eocene 

 of Wyoming, were really allied to the lemurs and perhaps 

 also to the marmosets, the lowest form of American monkeys, 

 but having a larger number of teeth than either. A number of 

 other remains of small animals from the same formation, pre- 

 viously supposed to be allied to the Ungulata, are now shown to 



