492 THE AGE OF MAMMALS 



favored by a dry or arid climate, even if cold. Dall ^ remarks that the eleva- 

 tion of the continental shelf under Behring Sea about 300 feet would 

 have laid bare an enormous level plain covering most of the present area 

 of Behring Sea. The diminished body of water in connection with the 

 prevalence of the northwest trade winds would have given to this region such 

 a dry climate as characterizes much of Siberia and the Yukon Valley in 

 Alaska to-day, which actually suffers from severe summer droughts. 



Vast shallow lakes of muddy water might, as now happens in the same 

 region, freeze solidly to the bottom and be covered with deposits of clay 

 from the spring freshets, a condition explaining the great ice lenses of the 

 'ground ice' formation. Certain mammals might have been trapped in 

 the quagmires formed by these clays. Finally, with the subsidence of the 

 coast and the return of a milder chmate, the ice lenses in the more northern 

 and colder regions, especially where protected by the clays, by the freezing 

 of the soil, and by the arctic vegetation, would be conserved to the present 

 day. 



Characteristic Mammals of the Third or Ovihos Zone 



Distribution of musk oxen. — Beside the extinct short-horned musk ox 

 (Syfnbos) found in Arkansas, remains of musk oxen are recorded ^ at Fort 

 Gibson, Indian Territory, in three localities in Missouri, in Trumbull County, 

 Ohio, at Big Bone Lick, Kentucky, in two localities in Pennsjdvania, at 

 Council Bluffs, Iowa, and near Salt Lake City, Utah. In every instance the 

 remains have been recovered either directly from glacial deposits or from 

 deposits that may be correlated with some stage of the Glacial Period. The 

 skull of a musk ox (Ovihos camfrons), discovered in part of the glacial terrace 

 near the Ohio River in West Virginia, one mile from Steubenville, was asso- 

 ciated with the shoulder blade of a mammoth of undetermined species. The 

 reasonable inference seems to be that the musk oxen moved southward 

 before the advancing ice, and then retreated northward to their present 

 areas of distribution. (See Fig. 214.) 



Cervalces. — An almost complete skeleton of an extinct moose was discov- 

 ered in 1884 in the shell-marl deposit under a bog at Mt. Hermon, New Jersey, 

 and described by Scott in 1885.^ Its occurrence so far south of the present 

 range of the moose points to a cold climate in New Jersey, but whether this 

 animal belongs to the Megalonyx or to the Ovibos Zone cannot be determined 

 at present. It is a remarkably long-limbed form, perhaps in adaptation 

 to its habitat in snowy regions. The unusual size of the lateral digits would 

 also favor the supposition of walking in the snow, although they may 

 have been an adaptation to swampy conditions. The antlers are large and 



1 Dall and Harris, op. cit., p. 266. 



2 Hatcher, .J. B., Discovery of a Musk Ox Skull {Ovibos cavifrons Leidy), in West Virginia, 

 near Steubenville, Ohio. Science, n.s.. Vol. XVI, Oct. 31, 1902, pp. 707-709. 



^ Scott, W. B., Cervalces americanus, a Fossil Moose, or Elk, from the Quaternary of New- 

 Jersey. Proc. Acad. Nat. Sci. Philadelphia, 1885, pp. 181-202. 



