THE PLIOCENE OF EUROPE, ASIA, AND NORTH AMERICA 353 



If not, it seems not improbable that they served as accessories to the great 

 claws to assist in rapid digging. 



The duplicidentate rodents are represented by the true hare (Lepus). 



Lower Pliocene mastodons. — The giant forms of the period are the long- 

 jawed, tetralophodont mastodons of the species Telralophodon campester 

 and T. euhypodon, both described by Cope. In the second species, T. 

 euhypodon,^ the symphysis of the jaw is abbreviated when we consider it in 

 relation to the large size of the inferior tusks, yet it cannot properly be 

 called ' brevirostral' ; the superior tusks are compressed distally; the in- 

 ferior tusks are large, cyhndrical, and retain the enamel band. The other 

 species, T. campester, embraces animals of larger size, with a very long 

 symphysis in the lower jaw, i.e. of more primitive ' longirostral' propor- 

 tions; the intermediate molars are tetralophodont, and the sixth molar has 

 six cross rows of tubercles, and a heel. 



Attention has been called above to the fact that the Lower Pliocene 

 mastodons of Europe embrace both the trilophodont and tetralophodont 

 types, and are believed to be short-jawed, or brevirostral, although this is 

 not to the present writer's knowledge certainly known. 



Carnivores. — The carnivorous enemies of this large herbivorous fauna 

 are still very imperfectly known. Among the canids there are two species of 

 ^lurodon. The jElurodon was as large as the modern wolf, but had a 

 short, heavy, mastiff-like head, and was distinguished from any living canids 

 by the cat-like construction of the carnassial teeth. There is some, 

 although not conclusive, evidence of the existence of an animal related to 

 the bear-dog (Dinocyon) and known as Borophagus. The survival of these 

 animals throughout the Pliocene of America as well as of Asia is rendered 

 probable by the occurrence of Dinocyon limb fragments in the Middle 

 Pliocene deposits (Blanco) of Texas. There is also some evidence of the 

 existence of true dogs of the genus Canis from rare and fragmentary 

 material. 



Lower Pliocene, Late Phase 



Snake Creek Formation (Ogallala) of Western Nebraska, 

 Neotragocerus Zone 



A more recent phase of the Lower Pliocene mammalian life of the region 

 of western Nebraska has recently been revealed in the discovery by an 

 American Museum party under Matthew and Cook - of the remains of a 

 large and varied fauna, including no less than fifty species of mannnals which 

 are in many respects intermediate in evolution between those of the 



1 Cope, E. D., The Proboscidia. Amcr. Natural., Vol. XXIII, no. 268, April, 1889, 

 pp. 191-211. 



^ Matthew, W. D., and Cook, H. J., Pliocene Fauna of Western Nebraska. Bull. Amer. 

 Mus. Nat. Hist., Vol. XXVI, no. 27, Sept., 1909, pp. 361-414. 

 2a 



