NOES 2.35 
been the last native to North America, the rear guard of the last 
migration of these animals across the region of Bering Straits to 
Asia before the land connection disappeared. There was a species 
of musk-ox together with sheep and bear. Descendants of these 
last three forms have by adaptive changes survived in these northern 
regions down to the present time. 
The relation that the fauna and flora north of the area occupied 
by glaciers bore to that in the region of the United States before, 
during, and after separation by the snow and ice fields; also the 
relation of forms in Alaska to those of Siberia, with the time and 
duration of the land connection across Bering Straits and their sub- 
sequent separation, form a complex problem, the solution of which 
will require the accumulation of much material. 
He summarizes his conclusions as follows: 
I. That while remnants of the large Pleistocene mammal herds 
may have survived down to the Recent period and in some cases 
their direct descendants, as the musk-ox, to the present, most of 
them became extinct in Alaska with the close of Pleistocene. 
II. The most rational way of explaining this extinction of ani- 
mal life is by a gradual changing of the climate from more temper- 
ate conditions permitting of a forest vegetation much farther north 
than now, to the more severe climate of today which subduing the 
vegetation and thus reducing the food supply besides directly dis- 
comforting the animals themselves, has left only those forms 
capable of adapting themselves to the Recent conditions surviving 
in these regions to the present. 
III. There are no facts to support the contention that the climate 
of the Arctic and sub-Arctic regions ever has been colder than it 
is at present. There are no phenomena presented in those regions 
that require a more severe climate than that now existing to account 
for them. There are no ice deposits in Alaska, except those of 
large glaciers that may be considered of Pleistocene age. There 
are no ice beds interstratified with the Pleistocene deposits of Alaska. 
IV. That the various forms of land ice, together with the de- 
posits of peat, now existing throughout the Arctic and sub-Arctic 
regions of Alaska belong to the Recent period and these deposits 
may be most conveniently and logically classified by their position 
with reference to the Pleistocene and Recent formations and the 
ice deposits cannot be differentiated satisfactorily into deposits of 
snow or of water origin by their physical structure and character 
alone. 
