EXTINCT MAMMALS OF ALASKA 
79 
conditions. Mr. Maddren urges that there are no facts to sup¬ 
port the contention that the climates of the Arctic and 
sub-Arctic regions ever had been colder than they are at 
present. He thinks that there are no phenomena presented 
by the past history of these regions that require a more 
severe climate than that now existing to account for them. 
There are no ice deposits in Alaska, he says, except those of 
large glaciers, that may be considered of Pleistocene age. 
There are no ice-beds, he continues, interstratified with the 
Pleistocene deposits of Alaska. Finally he argues that the 
various forms of land ice, together with the deposits of peat, 
now existing throughout the Arctic and sub-Arctic regions 
of Alaska, belong to the Recent Period, and that these deposits 
may be most conveniently and logically classified by their 
position with reference to the Pleistocene and Recent forma¬ 
tions, and that the ice deposits cannot be differentiated satis¬ 
factorily into deposits of snow or water origin by their 
physical structure and character alone.* 
A second Smithsonian expedition to Alaska was dispatched 
a few years later under Mr. Gilmore. He noticed that the 
scattered remains of Pleistocene animals occurred throughout 
the unglaciated region of Alaska and the adjacent Canadian 
territory in three distinct deposits, viz., in what is locally 
known as “ black muck,” which is accumulated in the valleys 
of the smaller streams, then in the silt and clays already 
referred to, and finally in the more recent fluvial and alluvial 
beds. The best-preserved remains were obtained in the muck 
deposits, and in these occurred certainly several examples of 
primary entombment. A magnificent skull with tusks of the 
mammoth was discovered in the muck forty-two feet below 
the surface, near Dawson, in the Yukon territory in north¬ 
western Canada. Mr. Gilmore f is convinced that the 
determinable species of mammals found are sufficient to 
show at once that they represent a typical Pleistocene 
fauna, some of them, such as the moose, caribou, musk ox, 
sheep, bear, and beaver, having persisted down to the present 
day. 
* Maddren, A. G., “ Smithsonian Exploration in Alaska,” pp. 65—66. 
t Gilmore, C. W., “ Smithsonian Exploration in Alaska,” pp. 26—38. 
