20 NEW YORK ZOOLOGICAL SOCIETY. 



ren Grounds, south and east of Cape Bathhurst, and the great 

 Arctic islands to the north of the continent, including Greenland, 

 where the local race has been described under the name of 0. 

 wardi. 



For some reason probably connected with the food supply, 

 it has disappeared from Alaska, and it is only recently extinct in 

 the Old World. The musk-ox probably came into America about 

 the same time as the bison, in fact all the Bovidae probably ar- 

 rived about the Middle Pleistocene, at the same time as Cervus. 

 In the recently discovered cave fauna of Arkansas a large species 

 of musk-ox has been found. 



MOUNTAIN SHEEP. 



With the mountain sheep we have a case very similar to that 

 of the bears and the wapiti. The genus Oms ranges throughout 

 Eurasia, and like Ursus and Cervus, has one outlying species in 

 North Africa. 



In Asia it extends eastward to Kamchatka, having, apparently, 

 its distributional centre in the central Asiatic plateau, where it 

 culminates in the great Marco Polo sheep, O. poll, whose horns 

 have a sweeping open spiral, and which is one of the most highly 

 prized trophies that can fall to a sportsman's rifle. 



The Eurasian sheep nearest in habitat and structure to the 

 American form is the Kamchatkan sheep, O. nivicola, and the 

 closely related O. sirensis of Mongolia. The great Oms am- 

 mon is also close. In fact, nearly all the Eurasiatic members of 

 the genus are very closely related to each other, and to the Ameri- 

 can forms. 



These latter, while obviously of Eurasian origin, have been 

 here long enough to split up into three good species and four sub- 

 species, chiefly characterized by their coloration, but in some 

 cases by their horn development. 



Beginning at the northwest, the Alaskan white sheep, O. dalli, 

 ranges throughout Alaska and the adjoining Rockies. The dis- 

 tribution of the closely related Fannin sheep, O. fannini, which 

 is a white sheep with dark saddle-patch and other dark markings, 

 is much more limited, and appears to be surrounded by the dis- 

 tributional area of O. dalli. Its value as a full species remains to 

 be determined. Both these sheep resemble the type big-horn of 

 the Rockies in the relatively close spiral of the horns, but do not 

 grow so large in bulk. 



