610 



ZOOLOGY. 



connects the deer family with the Bovidce, represented by 

 the sheep, goat, antelope, gazelle, and ox. 



The domestic sheep (Ovis aries Linn.) is not a natural 

 species, but an association of races whose specific origin is 

 obscure. Some authors regard the turf sheep of the stone 

 age of Europe as the ancestor of the domestic sheep, as forms 

 like it are now living in the Shetland Isles and in Wales. 

 It .was of small size, with slender limbs, and erect, short 

 horns. This sheep was supplanted by a curved, large-horned 

 form, the modern domestic sheep. This latter form is pos- 

 sibly the descendant of the Ovis argali Pallas, of Asia, which 

 in North America is represented by the Ovis montana Cuvier, 

 the Rocky Mountain sheep or big-horn (Fig. 530), still com- 

 mon on the less accessible summits along the upper Missouri 

 and Yellowstone Rivers, as well as the mountains of Wy- 

 oming and Montana. 

 In the same, though 

 higher and more inac- 

 cessible situations lives 

 the rare mountain 

 goat, Aptoceros monta- 

 nus Richardson, whose 

 horns are jet black and 

 polished, slender and 

 conical, like those of 

 the Swiss chamois. It 

 is found sparingly in 

 the higher summits of 

 the Rocky Mountains 

 and the Cascade range ; 

 an individual has within a few years been shot on Mount 

 Shasta, California. Passing by the gazelles and true an- 

 telopes we come to another characteristic American an- 

 imal, the musk sheep (Ovibos moscliatus Blainville, 

 Fig. 531), now confined to the arctic regions. A closely 

 allied species, Ovibos priscus of Riltimeyer, formerly during 

 the post-glacial period existed in England, France, and Ger- 

 many. Closely allied to the musk sheep is a fossil form 

 (Bootherium of Leidy) which is regarded by Rutimeyer and 



Fig. 529. Horns at different ages of the Prong- 

 horn Antelope, showing the hollow structure of 

 the horn when shed. After Hay*. 



