104 
ORIGIN OF LIFE IN AMERICA 
of the lower slopes of the mountains, and to it belong the 
typically American alpine species. They reach their greatest 
development in the southern portion of the Rockies. 
One of the most remarkable features, which I shall have 
occasion to draw attention to again in another chapter, is the 
occurrence in the Rocky Mountains of some species of plants, 
which reappear in the southern Andes, without being repre¬ 
sented either in the Mexican highlands or in the tropical 
Andes. Among these, Professor Engler * mentions the 
dwarf gentian (Gentiana prostrata), the mealy primrose 
(Primula farinosa), the hoary draba (Draba incana) and 
the alpine foxtail (Alopecurus alpinus). All these are 
common well-known European species. A few more have 
since been added by Professor Bray f This small group 
of species is of peculiar interest, not only because some¬ 
what analogous instances of distribution occur among insects, 
but also because this feature is by no means limited to 
mountain forms. In another chapter I shall allude to ; a 
number of species inhabiting the arid regions of south¬ 
western North America that likewise are quite unknown in the 
moist tropical and sub-tropical belts of country to the south, 
yet reappear in the extreme south of South America. Whether 
all these species possess particular facilities for dispersal 
over wide areas or whether former conditions of land and 
water were more suitable than they are at present for dis¬ 
persal will be discussed later on (p. 414). 
The fauna of the Rocky Mountains resembles the flora in 
its composition, except that among the higher animals, at any 
rate, the species are almost all endemic. Two kinds of animals 
in particular are associated with the Rocky Mountains in 
sportsmen’s minds, namely, the mountain sheep, or big-horn, 
and the Rocky Mountain goat. The former used to be known 
as Ovis canadensis. But from the systematic mill of the 
zoologist, as Dr. A. E. Brown $ puts it, have been produced' 
seven new species and sub-species, all very closely re¬ 
lated to one another. As already stated, the Kamchatkan 
* Engler, A., “Entwicklungsgeschichte,” IT., p. 256. 
t Bray, W. L., “ Relations of North American Flora,” p. 713. 
J Brown, A. E., “ Zoology of North American Big Game,” p. 69, 
