CHAPTEE XXIII. 



SUMMARY OF THE DISTKIBUTIOX, AND LINES OF MIGRATION, OF 

 THE SEVERAL CLASSES OF ANIMALS. 



Having already given summaries of the distribution of the 

 several orders, and of some of the classes of land animals, we 

 propose here to make a few general remarks on the special 

 phenomena presented by the more important groups, and to 

 indicate where possible, the general lines of migration by w^hich 

 they have become dispersed over wide areas. 



Mammalia. 



This class is very important, and its past history is much 

 better known than that of most others. We shall therefore 

 briefly summarise the results we have arrived at from our ex- 

 amination of the distribution of extinct and living forms of 

 each order. 



Primates. — Tliis order, being pre-eminently a tropical one, 

 became separated into two portions, inhabiting the Eastern and 

 Western Hemispheres respectively, at a very early epoch. In 

 consequence of this separation it has diverged more radically 

 than most otlier orders, so that the two American families, Cebidae 

 and Hapalidie, are widely differentiated from the Apes, Monkeys, 

 and Lemurs of the Old World. The Lemurs were probably still 

 more ancient, but being much lower in organisation, they 

 became extinct in most of the areas where the higher forms of 

 Primates became developed. Ptemains found in the Eocene 

 Ibvniation indicate, that the North American and European 



