490 THE AGE OF MAMMALS 



in gulches and valleys of the smaller streams; second, in the fine elevated 

 clays of the 'Yukon silts' and 'Kowak clays'; and third, in the more recent 

 fluvial and alluvial deposits.^ Of these the most remarkable is the 'ground 

 ice' formation of Dall, in which solid beds of ice of considerable thickness 

 take the place of rock strata, and are covered by beds of blue clay containing 

 numerous remains of Pleistocene mammals. The distribution of these 

 ground ice formations and of the ' Kowak Clays ' is plotted on the accom- 

 panying Alaskan map, which combines the results of Dall and of Quacken- 

 bush, the symbols indicating our present knowledge of the distribution of the 

 principal types of mammals. This distribution includes, beside the above, 

 bones recorded in river gravel deposits. In some of the clays the parts 

 preserved are so complete as to indicate that the animals were mired 

 entire, one such specimen with portions of the hair and wool having been 

 discovered by Quackenbush.^ 



Elephas primigenius, the hairy or northern mammoth. 



Elephas columbi (determination somewhat micertain). 



Mastodon americanus. 



Ovis (determination somewhat uncertain). 



Ovihos moschatus, the true musk ox. 



Ovihos yukonensis, an extinct species. 



Symhos tyrelli, with much smaller horns than Ovihos. 



Ovis montanus, the mountain sheep. 



Oreamnos, the mountain goat. 



Rangifer sp. ind., caribou, probably the 'barren ground' variety. 



Bison crassicornis, a long-horned species. 



Bison occidentalis, resembling the recent bison. 



Bison alleni, with long, slender, much curved horns. 



Alces, the moose {? Alces americanus). 



Equus, species indeterminate. 



Ursus, of the size of U. americanus. 



Canis. 



Castor, the beaver. 



Odohcenus, the walrus. 



Judging from the number of separate bones collected or examined by 

 Quackenbush, the mammoth was everywhere the most abundant animal, 

 the bison followed closely, the horse and caribou existed in lesser numbers, 

 and other mammals were comparatively scarce. That the country was 

 forested and the climate somewhat milder than that of the present time 

 seems to be proven by the fact that large trees have been found associated 



1 Gilmore, C. W., Smithsonian Exploration in Alaska in Search of Pleistocene Fossil 

 Vertebrates. Smiths. Miscel. Coll., part of Vol. LI, Washington, 1908. 



^ Quackenbush, L. S., Notes on Alaskan Mammoth Expeditions of 1907 and 1908. Bull. 

 Amer. Mus. Nat. Hist., Vol. XXVI, Art. Lx, Mar. 24, 1909, pp. 87-130. 



