SKELETON OF ARTIODACTYLA. 481 



most developed and chiefly serviceable in progression, answer to 

 the third and fourth digits of the pentadactyle foot : but in Sus 

 the homologues of the fifth and second are present ; whilst in 

 Dicotyles the fifth as well as the first toe are wanting in the hind 

 foot : in this the second toe is small ; the third and fourth are very 

 large^ and form a symmetrical pair, showing that the Artiodactyle 

 structure essentially prevails, although the toes, by the non- 

 development of the fifth, are, exceptionally, reduced to three in 

 number in the hind foot of the Peccari. 



In the CamelidcB, fig. 306, the scapula though longer than 

 in the non-ruminant Artiodactyles, . is broader, relatively, than 

 in horned Ruminants : its spine is produced into a short pointed 

 acromion : the coracoid is grooved below, or sub-bifid. The 

 humerus is weaker than in the Ox, stronger than in the Deer, 

 longer relatively to the rest of the limb than in the Giraffe : the 

 great tuberosity does not rise above the head : the ridge upon 

 the outer condyle is less marked. The ulna has coalesced with 

 the radius, and appears to be represented only by its proximal 

 and distal extremities. The carpal bones have the same number 

 and arrangement as in ordinary ruminants, but the pisiforme is 

 proportionally larger. There is no trace of the digits answering 

 to the first, second, and fifth in the pentadactyle foot : the meta- 

 carpals of those answering to the third and fourth have coalesced 

 to near their distal extremities, which diverge more than in the 

 ruminants, giving a greater spread to the foot, which is supported 

 by the three phalanges of each of those digits. The last phalanx 

 deviates most from the ordinary form, by its smaller j^roportional 

 size, rougher surface, and less regular shape : it supports, in fact, 

 a modified claw rather than a hoof. The ilium, in proportion to 

 the ischium, is longer than in the Hippopotamus. In the femur, 

 the chief deviation from the ordinary Ruminant type is seen in the 

 position of the orifice of the canal for the medullary artery, which 

 enters the back part of the middle of the shaft, and inclines 

 obliquely upward. The fibula is represented by the irregularly- 

 shaped ossicle interlocked between the outer side of the distal end 

 of the tibia and the calcaneum. The scaphoid is not confluent 

 with the cuboid as in the normal Ruminant: the rest of the hind- 

 foot deviates in the same manner and degree from that type, as 

 does the fore-foot. In both metacarpals and metatarsals, notwith- 

 standing the intimate blending of the two bones apparent exter- 

 nally, their medullary cavities arc distinct : the canal of the 

 medullary artery enters the back part of each, above the middle, 

 and ascends obliquely to its respective cavity. 



VOL. II. II 



