I'kikkson : OsTEoi-ocv oi' ()xvi).\(. lYi.us. 455 



of the radius is narrow. 'I'he external articular facet for the humerus 

 is much larger than the internal, and, as in recent genera, it is not 

 continuous with the superior border of the sigmoid notch. The inter- 

 nal facet passes upward without interruption to the summit of the supe- 

 rior process. The two facets are concave and are divided by a rounded 

 ridge which also extends uninterruptedly to the upper extremity of 

 the sigmoid notch. The olecranon process is moderately long, com- 

 paratively light, and much compressed laterally, and is directed back- 

 wards and upwards from the sigmoid notch. In having the groove 

 on the anterior face well developed for the extensor tendon Oxydacty- 

 liis differs entirely from the recent camel and the llama. Poebrothe- 

 riiiin has also this groove well developed. The truncated superior end 

 of the olecranon process of Oxydactylus longipes is comparatively 

 lighter than that of the recent genera. The proximal half of the 

 ulnar shaft is concealed by the radius when viewed from the front. 

 Midway the shaft of the ulna appears on the external side of the radius 

 and forms a sharp ridge thus broadening the shaft composed of the 

 combined radius and ulna which is decidedly wider distally than proxi- 

 mally. In the skeleton of Lama huanaco, here used for comparison, 

 the ulna like that of the camel has a more external position through" 

 out the entire length of the radial shaft. This may be due to indi- 

 vidual variation, since Scott says that the ulna in the llama is almost 

 entirely posterior in position.'- In the type the bicipital tuberosity is 

 small as in Po'ebrotherium and occupies the internal border immedi- 

 ately below the head as in the recent forms. Distally there are three 

 distinct facets which are more nearly ecpial in width than in the recent 

 camel and the llama. The median and external facets are propor- 

 tionally wider than in the latter genera. The three facets are more 

 oblique to the transverse axis of the shaft than they are in the llama. 

 The scaphoid articulation is concave anteriorly where it is more ele- 

 vated than the convex posterior part, which is carried high up on the 

 posterior face of the radius, conditions similar to those seen in the 

 recent genera. The lunar articulation is wider anteriorly than pos- 

 teriorly and presents a subtriangular facet, which is well separated 

 from the scaphoid and cuneiform facets by high ridges. Like the 

 scaphoid the lunar facet is concave in front and convex behind, and is 

 reflected on the posterior face of the radius but in a lesser degree. 

 The cuneiform facet is proportionally narrower' than in the llama, and 



^^Joiirii. Morph., Vol. V, No. I, p. 32, 1891. 



