PRONG-HORN ANTELOPE 
113 
“ Deep River ” deposits of' Montana in middle or lower 
Miocene, and persisted until the Pliocene. During the latter 
period several new genera, viz.: Capromeryx, Platatherium 
and Leptotherium, branched off from the ancestral stock, and 
made their way into newly-opened areas. The last two have 
occurred in recent beds in Brazil, the other in Nebraska. 
Thus the family Antilocapridae to which the recent prong¬ 
horn and all these fossils belong, originated in America and 
never left it. 
Among the birds of the Rocky Mountains the dippers are 
very characteristic. They are quite unrepresented on any 
of the eastern mountain systems, being also absent from 
Greenland and Labrador. In the Old World they are more 
or less confined to the mountains, but not nearly to the same 
extent as in America. In my “ European Animals ”* I have 
already cited Dr. Stejneger’s interesting article on the geo¬ 
graphical distribution of the dippers (Cinclus), and I may 
again briefly summarise the results of his studies. He places 
the origin of the genus on the great plateau adjoining 
northern India. At the dawn of the Tertiary Era the species 
radiated from this centre east and west. America being then 
connected by land with northern Asia, the ancestors of the 
present dippers had special facilities for crossing to the New 
World from Asia. They are supposed to have spread since 
along the Rocky Mountains and Andes to the very furthest 
end of South America. Dr. Stejneger’s theoryf certainly ex¬ 
plains the existing range of Cinclus in a satisfactory manner, 
but there seems to me still another view of looking at the 
problem. If, as I believe, the Atlantic Ocean was bridged 
over by land in the direction of southern Europe in early 
Tertiary times, it is possible that the dippers may have been 
introduced into the New World in that manner. At any rate, 
the problem is worth considering from that point of view, 
when the dippers come to be worked ou,t in .a thoroughly 
systematic way. Among the older forms of both animals and 
plants there are in western America a surprisingly large 
number of groups which are closely related to European ones. 
* Scharff, R. F., “European Animals,” p. 200. 
t Stejneger, L., “ Geographical Distribution of Cinclus,” p. 425. 
L. A. 
I 
