NO^ES ON THE CANID^E OF THE WHITE RIVEK OEIGOCENE. §§5 



a very narrow surface which appears to be destined for articulation with the head of 

 the fifth metacarpal. 



The pisiform differs very decidedly in shape from that of Cards. This carpal is 

 small and light ; its proximal (i. e., articular) end is greatly depressed, but much extended 

 transversely (in the existing genus the principal diameter of the jn'oximal end is the 

 vertical one) and the facets for the pyramidal and ulna are correspondingly broad- 

 ened transversely and narrowed vertically. The pyramidal facet is the larger of the 

 two and is quite deeply concave, while that for the ulna is small and nearly plane ; the 

 two facets together form an acute angle and are separated only by an inconspicuous ridge. 

 The distal end of the pisiform is moderately expanded, but in the vertical dimension, so 

 that the proximal and distal expansions are almost at right angles with each other. 

 Between the two exj>ansions the body of the bone is much contracted and very slender, 

 which is in marked contrast to the shape seen in Canis. 



A so-called " radial sesamoid " appears to have been present; at least, there occurs 

 in the same block of matrix through which the carpals of one individual were scattered, 

 a small, irregularly wedge-shaped bone, to which I can give no other interpretation. 

 Assuming that this reference is correct, we find in the relative size and shape of this bone 

 another resemblance to such viverrine genera as Herpestes, Cynogale and Paradoxurus, 

 etc. The radial sesamoid also occurs in Canis, at least in certain species, but is very 

 minute. 



The trapezium is very small and differently shaped from that of Canis; its princi- 

 pal dimension is the dorso-palmar, while the transverse diameter is the least. The sur- 

 face for the scaphoid, which in Canis is a very oblique, convex facet, is in Cynodietis 

 entirely proximal in position and nearly plane, and there is no such large concave facet 

 for the trapezoid on the ulnar side as in the modern genus ; the distal facet for the head 

 of the first metacarpal is less distinctively saddle-shaped than in the latter. In view of 

 the well-developed pollex, the small size of the trapezium is somewhat surprising. 



The trapezoid is shaped very much as in the existing dogs, but with certain minor 

 differences, especially noticeable in the A r ery small vertical diameter and in the thinning 

 of the bone to an edge on the ulnar side. The proximal end bears a simply convex facet 

 for the scapho-lunar, while the distal facet, for the second metacarpal, is very slightly 

 saddle-shaped ; on the palmar side the trapezoid contracts to a point. 



The magnum is small and that portion of it which is visible from the dorsal side, 

 when all the carpal elements are in their natural positions, is minute, especially in its 

 proximo-distal dimension. In shape the magnum does not differ materially from that of 

 the recent dogs, but the proximal surface is narrower and rises more abruptly to the 

 "head," and on the palmar side the bone broadens out in a fashion not repeated in Canis. 



