458 Annals of the Carnegie Museum. 



cent camel. Proximally the magnum articulates with the lunar and 

 scaphoid. The facet for the former is regularly convex and meets 

 the concave lunar facet. The latter is flat and irregularly triangular 

 in outline. The cavity for the trapezoid is nearly rectangular and it 

 more nearly resembles that of the camel than the llama. In the latter 

 genus the cavity for the trapezoid is a very oblique opening, with walls 

 slanting upwards and inwards. The ulnar side is excavated and has 

 two facets, one anterior and one posterior, both articulating with the 

 unciform. The anterior facet is continuous with the lunar facet, 

 which is situated above, without a distinct dividing ridge, as is seen 

 in the llama and the recent camel. The posterior facet is located on 

 the free end of the tubercle on its posterior-ulnar side. Distally the 

 magnum has one single broad triangular and flat articulation, some- 

 what recurved posteriorly, forming a blunt beak for articulation with 

 metacarpal three. 



The Uiicifonii. — The unciform in the type (No. 918) is narrow and 

 long. The great development of the posterior decurved hook-like 

 process greatly increases the length of the bone. Proximally the un- 

 ciform has two facets, the lunar and the cuneiform, which are divided 

 by a high sinuous ridge. The lunar facet is the larger and is deeper 

 than is that of the llama. The cuneiform facet is long, narrow and 

 irregularly curved. There are three facets on the radial side of the 

 unciform, the two superior facets articulate with the magnum, and the 

 inferior facet meets the external side of the proximal end of the third 

 metacarpal. The deeply excavated pit which appears in front of the 

 tubercle on the radial side in O. longipcs is represented only by a slight 

 cavity in the llama. In the camel this cavity is somewhat deeper but 

 not so deep as in O. h>>!_i:;ipcs. Externally the unciform is rounded and 

 rugose. The distal articulation for metacarpal IV is slightly concave 

 and occupies the entire distal surface of the bone. The unciform of 

 O. lougipes more nearly resembles that of the recent camel than that of 

 the llama. The greatly developed posterior hook on the unciform in 

 Oxydactylus is generally characteristic of the Loup Fork camels. 



The Metacarpals. — (PI. VIII, Figs. 2 and 3.) On the sides of the 

 functional third and fourth metacarpals of (No. 8S6) there are small, 

 flat, rugose ossicles, representing metacarpals II and V. Metacarpals 

 III and IV are entirely separated and proportionally more elongated 

 than in the recent genera. The upper two thirds of the shaft is later- 

 ally much compressed. The distal portion is D-shaped in cross-sec- 



