302 THE AGE OF MAMMALS 



first amphicyon-like animal recognized in America is the species A. amer- 

 icarius, described by Wortman ^ in 1901, one of a number of somewhat 

 atypical forms to which Cope gave the name Borophagus, animals differing 

 from the typical amphicyons of Europe. As in the Old World, these are 

 truly the giant carnivores of the period, some of them rivaling the largest 

 existing bears in size. Thus the D. gidleyi of the Clarendon beds of Texas 

 has a head as large as that of the great brown or Kadiak bear of Alaska. 

 The rodents of this period include squirrels, marmots, and mylagaulids, 

 gophers, murids, leporids, and castorids. Among the last is the species 

 Eucastor (Dipoides tortus), which presents a resemblance to the giant Cas- 

 toro'ides of the Pleistocene.' 



Miocene History of American Deer 



All the New World or American deer (Odocoileus, Mazama, etc.) are 

 known to stand well apart from the Old World deer (Cervus) in two impor- 

 tant characters, namely, the absence of the brow tine of the antler and in 

 the preservation of the distal portion of the lateral metacarpals. They are 

 thus termed tele metacarpal, while Cervus is termed plesiometacarpal because 

 the proximal portion of the metacarpals is preserved. It appears certain 

 that the Odocoileus and Cervus phyla have been separated since very ancient 

 times. According to the observations of Matthew ^ the diminutive Lepto- 

 meryx of the American Lower Oligocene is an extremely unspecialized 

 ruminant related to the primitive American cervids. It is possible that 

 through the Miocene Blastomeryx it may be a direct ancestor of the deer ; 

 Blastomenjx is analogous to the Miocene deer of the Old World, being 

 armed with powerful canine tusks in the Lower Miocene stage {B. priinus), 

 and not acquiring horns, 'antlers,' until Upper Miocene times (B.antilo- 

 pinus Scott, B. horealis Cope). The Dromomeryx of Douglass is also to be 

 considered in this connection. The Pliocene stage of the browsing Ameri- 

 can deer with simple antlers has not yet been chscovered; it should be 

 somewhat more primitive than the North American Odocoileus and resem- 

 ble rather the South American deer (Mazama) which occurs in Pleistocene 

 and recent times in that country. 



1 Wortman, Amer. Jour. Sci., 1901. 



2 Matthew, W. D., A Horned Rodent from the Colorado Miocene. "With a Revision of 

 the Mj'lagauli, Beavers, and Hares of the American Tertiary. Bull. Amer. Mus. Nat. Hist., 

 Vol. XVI, Art. xxii, 1902, p. 304. 



3 Matthew, W. D., Osteology of Blastomeryx and Phylogeny of the American Cervida. 

 Bull. Amer. Mus. Nat. Hist., Vol. XXIV, Art. xx\T[i, June 30, 1908, pp. 535-562. Speaking 

 more fully. Dr. Matthew's theory is that there was a common North Asiatic center of evolution 

 which contributed to Europe and North America, respectively, various stages in the evolution 

 of the deer. 



