THE PLIOCENE PERIOD 



843 



their deployment into present orders, and very generally into 

 present genera. They were also represented by many genera and 

 species which are now extinct. A list of Pliocene families would 

 be little more than a catalogue of living ones. The evolution of 

 the horse was advanced to the existing genus Equus. Giraffes and 

 giraffe-like animals, some of them of great size, invaded southern 

 Europe and Asia, coming probably from Africa. 



The giants of the period were the proboscidians. The extinct 

 Dinotherium was widely distributed in Europe and has been found 



Vig. 558. Teeth of elephant (Elephas primigenius) , with the transverse 

 ridges differentially worn, showing dentine in the center, the enamel, 

 which forms the crenulated loops, supported by dentine within and 

 cement without. (Owen and Metcalfe.) 



in India, but is not known to have reached America. Mastodons 

 seem to have occupied all the continents, but it is doubtful whether 

 the elephant reached America before the Pleistocene. They 

 appear to have flourished in Europe, and with the associated rhinoc- 

 eroses and hippopotamuses, gave to the European fauna an 

 African aspect. 



The carnivores of both continents throve and perhaps gained 

 on the herbivores; at any rate they put a severe tax on the herbiv- 

 ores, forcing further progress in the line of alertness, sagacity, speed, 

 and defense, and gaining similar qualities themselves. The rodents 

 appear to have held about their present place relatively. 



