590 



migrated from Central America by three avenues — i. e., the Pacific coast, the 

 central plateau of the Cordilleras, and the Atlantic coast — no one will proba- 

 bly deny. As regards the present arctic Fauna, which is truly circumpolar 



and scarcely more marked in America than Europe-Asia, and has alpine out- 

 liers on the alpine summits of the Ural and Altai ranges of Asia, the Alps 

 of Central Europe, and the mountains of Scandinavia, as well as the elevated 

 coasl of the Labrador plateau and the alpine summits of the Alleghany and 

 Rocky Mountains (including the Cascade range and Sierra Nevada of the 

 1'acilic coast), we are forced to believe that they have originated in circum- 

 polar lands, and have migrated southward cotemporaneously with the advance 

 southward of the glacial climate. It is not improbable that during the height 

 of the glacial period, when it prevailed over a large portion of the north 

 temperate zone, the number of species of insects were greatly in excess of 

 what it is at present, and that the existing arctic land-fauna is but a remnant 

 of what it was in the height of the Quaternary period. As regards the origin 

 of this Quaternary land-fauna, we are naturally led to conclude that it must 

 be the ancient inhabitants of the Tertiary continent of Arctic America and 

 Europe-Asia, of which the Arctic-American Archipelago, Greenland, and Spitz - 

 bergen are the remnants. This view is borne out by the fact that not only 

 Tertiary, but even several Cretaceous forms of marine invertebrates, are still 

 living at great depths in the arctic and north temperate seas. 



We are now restricted to a consideration of the origin of our north tem- 

 perate insect-fauna. Here absolute facts are wanting, as no fossil insects 

 common to Temperate and Arctic America have yet been found, and we are 

 thrown back on the facts and speculations afforded by palseontological bot- 

 anists, referring the reader for the facts as to the identity of certain species 

 in the Miocene Tertiary plants of Europe with those of Spitzbergen and 

 Arctic America to the writings of Heer, who shows that the Miocene "flora 

 of Europe had almost entirely an American character",* and to the results of 

 the studies of the Tertiary and Cretaceous flora of North America by Profes- 

 sor Newberry, and more especially those of Mr. Lesquereux in Hayden's 

 Annual Report of the United States Geological Survey of the Territories for 

 1872, and his subsequent reports and works published by the Survey. 



The results of these studies confirmed certain speculations previously 



* "Novdenskiold, The former Climate of the Polar Regions", iu Geological Magazine, Loutlou, 

 1875: American Naturalist, vol. x, 358, L876. 



