1900.] STRUCTURE OF THE MUSK-OX. 695 



concave interior surface. Through this arrangement the plantar 

 surface of the foot becomes concave, and in the middle there is a 

 broad opening between both hoofs. This opening is about as broad 

 as half the transverse breadth of each hoof measured separately. 

 Through this opening or fissure between the hoofs, hair, growing 

 between the fingers, protrudes to the lower surface of the foot, 

 which otherwise of course is naked. But the hair of the leg 

 hangs down on the hoofs, so that it is only a rather small portion 

 of them anteriorly which is visible. Posteriorly this fissure ia 

 terminated by a transverse pad which very firmly unites both hoofs 

 all the way to the treading surface, and consequently shares in 

 supporting the animal. 



The hoofs are a little irregular in shape, but not much so ; and it 

 can hardly be said that one hoof is more pointed thau the other, 

 because both are almost equally rounded. The fore hoofs are a 

 little longer than those of the hind legs, so that in an adult bull 

 the former measure about 12 cm. in length and the latter about 

 10 cm. 



From what has been said above, it will be seen that the shape of 

 the hoof is very different from that of the hoof of Bos and still more 

 from the narrow pointed hoofs of the Caprinee. In these animals 

 the toes are not so closely and firmly connected posteriorly as in 

 Ovibos. It seems more than probable that the shape of the hoofs 

 of the Musk-ox is an adaptation acquired secondarily ; and such a 

 statement is plainly confirmed on comparing the similarly broadly 

 rounded hoofs of the Reiudeer, which lives under similar circum- 

 stances to the Musk-ox, with the pointed hoofs of other Deer. 



The lateral hoofs of the Musk-ox are also comparatively large, 

 and have a very characteristic shape and aspect because the vertical 

 " Krallenplatte " does not together with the " Krallensohle," to 

 use Boas's terminology l , form an even cap over the rudimentary 

 phalanges, but grows out so that it protrudes a good deal beyond 

 the latter. This gives the lateral hoofs an irregular appearance as 

 if they were torn. Although they are broad the lateral hoofs are 

 not prolonged in such a way as in the Reindeer, and consequently 

 the convergence with the latter animal is not extended to these 

 parts. 



Sect. 3. — Description of the Skull of the Musk-ox. 



The osteology of the Musk-ox has been carefully described by 

 Owen, Riitimeyer, Dawkins, and others. A renewed description 

 of already known facts is consequently unnecessary, and it is not 

 my intention to give one on this occasion. But I will proceed 

 to a discussion of the characteristics of the Musk-ox skull based 

 on a compai-ison with other forms, and through this I hope to 

 bring forward some points which have been hitherto neglected or 

 misinterpreted. 



1 Boas, " Zur Morphologic der Wirbelthier Kralle," Morph. Jahrb. xxi. 1894. 



