SKELETON OF ARTIODACTYLA . 



483 



in the Clievrotains. The chief part of the ulua, ib. 3, is its com- 

 pressed olecranon : the slender shaft may be continued to the 

 carpus, as in MoschidcB, most Antelopes, Sheep, the Elk, the 

 Rein-deer, fig. 311; the Fallow-deer, and the common Ox. In 

 the Chevrotains it longest maintains its individuality : in the 

 Musk-deer and Elk the distal extremity coalesces with that of 

 the radius ; in the Rein-deer the shaft, also ; in the Ox this is so 

 confluent as to be hardly traceable from the olecranon to the 

 styloid extremity. In the Giraffe the ulnar shaft is interrupted 

 at its lower third, but the distal end reappears, as the * styloid 

 process,' but is connate with the distal epiphysis of the radius. 

 The radius and ulna are so interlocked that the fore-foot is kept 

 ' prone,' or with the surface answering to ^ palm ' 

 turned back and downward : there is a narrow cleft 

 at the upper part of their line of union, and some- 

 times a second lower down. In the carpus the usual 

 four bones of the proximal row remain distinct : in 

 fig. 330, A, c, 4 is ' scaphoides,' 5 lunare, 6 cuneiforme, 

 7 pisiforme : the distal row consists of the ' trape- 

 zoides,' a, in some, and in all of the ' magnum,' 8, sup- 

 porting the moiety of the metacarpal answering to the 

 ' third ' one of the pentadactyle foot, and the unci- 

 forme, 9, supporting the moiety answering to the 

 ' fourth ' metacarpal. These metacarpals early coa- 

 lesce into a single '^ cannon-bone : ' but a longitudinal 

 section, as in fig. 331,^ shows the medullary canal of 

 each distinct, in Megaceros, as in most Ruminants ; 

 in a few, e.g. the Yak {Bos grunniens) the septum 

 becomes partially absorbed.^ Longitudinal grooves 

 at the fore (fig. 330, A, lo) and back parts of the 

 cannon-bone, with antero-posterior perforations, are 

 the outward signs of the original separation : they are 

 most strongly marked in the Chevrotains ( Truf/uliis) ; and the 

 severance persists in the Water-Musk {Hycemoschus) as in the 

 extinct Dichodons, Anoplotheres, and Microtheres. Each moiety 

 of the cannon-bone has its distinct distal trochlea, fig. 331, «, h, 

 which is traversed by a median ridge, c, from before backward. To 

 each trochlea articulates a proximal phalanx, fig. 330, A, ii, sup- 

 porting a middle, 12, and this an unequal phalanx, 13, of a triedral 

 conical shape, modified to be sheathed in a hoof; the unsymmetry 

 of each hoof being such as to form a symmetrical pair. They re- 

 semble the single hoof of the horse cleft in twain : whence the 



Section of a 

 metacarpal of 



Megaccros. 



XCVI'. 



xcir. p. 260, no. 1162. 



lb. vol. ii. p. 628, no. 3852. 



