294 THE AGE OF MAMMALS 



tops of trees is conclusive evidence of increasing arid conditions and 

 lengthening summer droughts which would render an adaptation of this 

 kind of great survival value. Of the more conservative or typical 

 grazing camels with relatively short, limbs and sul)-hypsodont grinders 

 the characteristic forms are Miolabis, which succeeds the Lower Mio- 



Fig. 146. — Skeleton of the deer-antelope Mcrycodus osborni. In the American Museum of 

 Natural History. After Matthew. 



cene Protomeryx, and Protolahis, which includes certain long-headed 

 forms, readily distinguished from its successor Procamelus by the pres- 

 ence of a full set of upper incisor teeth and by its separate or 'split' 

 metapodials. 



The presence of numerous small-horned and hornless, grazing and brows- 

 ing ruminants lends an entirely new aspect to the plains and forest-border 



