156 THE MAMMALIA. 



rates from the primitive selenodont branch in the 

 Eocene probably through the genus Parameryx. In 

 the Miocene, we find in Poebrotherium and some 

 nearly allied forms, unmistakable indications that 

 the cameloid type of Ruminant had already become 

 partially specialised, although there is a complete 

 series of incisor teeth, and the metapodial bones 

 are distinct. In the Pliocene the camel tribe (in 

 America) was, next to the horses, the most abun- 

 dant of the larger mammals. The line is continued 

 through the genus Procamelus, and perhaps others, 

 and in this formation the incisors first begin to 

 diminish and the metapodials to unite. In Post- 

 Tertiary we have a true Auchenia represented by 

 several species, and others in South America, where 

 the alpacas and llamas still survive. From the 

 Eocene almost to the present time North America 

 has been the home of vast numbers of the Camelidae, 

 and there can be little doubt that they originated 

 there and migrated to the Old World.' * 



1 Cope, in 1877, gave a fuller account of these opinions. The 

 Miocene Poebrotherium possesses of grinders p. 4, m. 3. The two 

 elongated metapodials have not coalesced ; seven tarsals. Then 

 comes Protolabos still with p. 4, m. 3 ; the last molar is more 

 prismatic. The incisors also are still there in full number, but 

 fall out readily. Procamelus is the first to show incisors like 

 our present camel, yet still p. 4, m. 3. The side rudiments 

 of the metatarsals of Po&brotherium have disappeared, hence the 



