BOVIDE 
355 
widely separated and much larger than the posterior pair. The 
Bharal, however, resembles the Goats in having an oblong basi- 
occipital, with the posterior tubercles larger and more prominent 
than the anterior ones, both being situated in the same antero- 
posterior line. These transitions towards the caprine type are, 
however, not sufficient to support the view that the Bharal should 
form the type of a distinct genus (Pseudois), more especially since 
some of the typical Sheep, like 0. canadensis, have the lachrymal 
fossa of the skull very much reduced in size. 
The distinction of the various permanent modifications under 
which wild Sheep occur is a matter of considerable difficulty. Trivial 
characters, such as size, slight variations in colour, and especially 
the form and curvature of the horns, are relied upon by different 
zoologists who have given attention to the subject in the discrimina- 
tion of species, but no complete accord has yet been established. 
The most generally recognised forms are enumerated below. 
The geographical distribution of wild Sheep is interesting. The 
immense mountain ranges of Central Asia, the Pamir and Thian- 
Shan of Turkestan, may be looked upon as the centre of their 
habitat. Here, at an elevation of 16,000 feet above the sea-level, 
is the home of the magnificent Ovis polt, named after the celebrated 
Venetian traveller Marco Polo, who met with it in his adventurous 
travels through this region in the thirteenth century. It is remark- 
able for the great size of the horns of the old rams and the wide 
open sweep of their curve, so that the points stand boldly out on each 
side, far away from the animal’s head, instead of curling round 
nearly in the same plane, as in most of the other species. A Sheep 
from the same region, in which the horns retain their more normal 
development, has received the name of 0. karelini, but, according to 
Mr. W. T. Blanford,! is not distinct specifically from 0. poli. East- 
ward and northward is found the Argali (0. argali), with a wide and 
not very well determined range; it formerly occurred in the Altai, 
but is now found in Northern Mongolia. Still farther north, in the 
Stanovoi Mountains and Kamschatka, is 0. nivicola, and away on 
the other side of Behring’s Strait, in the Rocky Mountains and 
adjacent highlands of western North America, is the “Bighorn” 
or Mountain Sheep (0. canadensis), the only member of the genus 
found in that continent, and indeed—except the Bison, Musk-Ox, 
Mountain Goat (Haploceros), and the Prong-buck (Antilocapra)— 
the only hollow-horned Ruminant, being like the rest obviously 
a straggler from the cradle of its race. The two last-named 
species are nearly allied, and are characterised by the slight 
development of the ridges on their horns and the very shallow 
lachrymal fossa. Turning southward from the point from which we 
started, and still a little to the east, in Nipal and Western Tibet, 
1 Proe, Zool. Soc. 1884, p. 326. 
