440 



THE AGE OF MAMMALS 



fluences, still include no arctic, tundra, or steppe types. Among the still 

 surviving forms, which, however, disappear during this period, are the 

 machaerodonts and the tapirs. The camels, which no longer occur in the 

 east nor in the forested regions, appear to survive in California and in 

 the plateau regions of the southwest. The peccaries are represented by 

 Mylohyus. The mylodont sloths seem to have given way gradually to 

 the giant sloths {Megahnyx). Giant bisons {B. latifrons) abound in the 

 east. Among the rodents the porcupines (Erethizon) -and the marmots 



(Marmota) appear. Precursors 

 of the musk ox appear (Eucera- 

 therium). The moose (Alces) 

 is frequently recorded, and the 

 true deer (Cervus) perhaps 

 arrives very late. There is still 

 no trace of the reindeer {Ran- 

 gijer) nor of the musk ox. 



III. Third or Ovihos-Rangifer 

 Zone of the plains and forests 

 (see p. 486). The third mam- 

 malian fauna is apparently that 

 of the final glacial advance and 

 perhaps of a cold, dry loess 

 period. It includes the musk 

 ox (Ovibos), which advances 

 into the Middle States (Fig. 

 214). The mastodon is the 

 dominant form in the forests 

 of the East. The true northern 

 mammoth (Elephas primigenius) 

 appears and spreads as far south 

 as the city of Washington (see 

 Fig. 189, C). The reindeer 

 {R. caribou) is widely distrib- 

 With the remains of the mammoth are 

 The saber-tooth tigers have 



Fiu. 190. — Molars of (.4) the northern mam- 

 moth, Elephas primigenius, (B) the Cohimbian mam- 

 moth, Elephas columbi, (C) the Imperial mammoth, 

 Elephas imperator. In the American Museum of 

 Natural History. 



uted in the Middle States 



associated those of several species of bison. 



disappeared. 



IV. Fourth or Cervus Zone. The fourth fauna is the prehistoric 

 fauna of the forests of the East and West, of the prairies, and of the great 

 plains and arid region. It is characterized by the very wide distribution 

 of the wapiti (C. canadensis), or Old World deer. It includes all the mam- 

 mals which the early settlers found on this continent. All the horses, tapirs, 

 proboscideans, and other exotic mid-Pleistocene forms have disappeared. 



Succession of elephants or mammoths. — The three great elephants of 

 Upper Pliocene and Pleistocene times in North America, although partly 



