No. i.] OSTEOLOGY OF PCEBROTHERIUM. 37 



metacarpal. The distal trochlea is very narrow, hardly expand- 

 ing at all beyond the shaft, and is simply convex from before 

 backwards. The carina is entirely confined to the palmar side, 

 and is less prominent even than in the existing members of the 

 family. In position, it is slightly to the medial side of the 

 middle line. Besides the carina the elevation of the medial and 

 external borders produce keels which are much sharper and more 

 prominent than in the llama. 



Mc. IV is the counterpart of mc. Ill, but is decidedly more 

 slender and flattened in its proximal half. Its head is decidedly 

 narrower, and its apparent breadth is reduced by the overlapping 

 process from mc. Ill to the unciform. On the ulnar side of the 

 proximal end there is a deep excavation in which lies the rudi- 

 mentary fifth metacarpal. 



Mc. V is a very much reduced and flattened scale, even 

 smaller than the rudimentary second digit, and is attached to 

 the side of the unciform by a minute facet. 



The phalanges (PI. Ill, Figs. 48, 49) of the manus are very 

 different from those of the recent Tylopoda, and would seem to 

 indicate that Pcebrotherium possessed a foot like that of the 

 typical ruminants ; not the broad pad or cushion which charac- 

 terizes the existing forms. The phalanges of the first row are 

 long and slender, but much shorter, relatively, than in the llama ; 

 nor are the proximal and distal ends so much expanded as in that 

 animal : their shape is likewise more asymmetrical, owing to the 

 less degree of divergence of the toes. In the true ruminants 

 the strong degree of convergence produces decided asymmetry 

 of the phalangeal articular surfaces. In Pcebrotherium the 

 groove for the carina of the metacarpals is a mere emargination 

 of the posterior edge. The phalanges of the second row are 

 even more unlike those of the recent genera, in that they are 

 short and much compressed, but of considerable antero-posterior 

 diameter, while in the camel and llama they are broad and much 

 depressed and flattened. The ungual phalanges resemble those 

 of the antelope and deer much more than they do those of the 

 recent Tylopoda ; they are long, high, and pointed, somewhat 

 rounded on the outer, but quite flattened on the medial surfaces. 

 These phalanges are sufficient to show that Pcebrotherium could 

 not have had anything more than a rudimentary pad. 



