Peterson : ().siKoi,of;v or Oxvdacivlus. 463 



The Patella. — There is no patella with the type, but it is present 

 in another skeleton (No. 562), where it is thinner, broader, and much 

 shorter than is that of the llama. 'I'he superior border is the broadest 

 and the outline is that of a long triangle with the apex directed 

 downward. 



The Tibia. — The tibia in O. h>/igipes is longer than the femur, 

 while in the camel the femur is much the longer bone of the two. 

 In the llama the two bones are of equal length. In Po'cbrotheriiitn 

 the tibia is apparently longer than the femur. The shaft is long, 

 slender and straight, the lower half being suboval in cross-section. 

 Proximally there is a great expansion equaling that in the llama. 

 The articulations for the femoral condyles are broad laterally, slightly 

 convex antero-posteriorly, and, as in the llama, the external facet is 

 the larger, and is separated from the internal by the bifid spine. The 

 cnemial crest is comjiaratively heavier and extends lower down on the 

 shaft than does that of the llama and the camel. Distally the ex- 

 ternal facet for the astragalus is proportionally wider, and the internal 

 narrower than that of the llama, resembling that of the camel more 

 closely in this respect. In the latter the internal malleolus is placed 

 anteriorly and in such a way as to present a constriction on the an- 

 terior half on the internal facet, similar to that found in O. lougipes. 

 In the llama the external facet is entirely without this constriction. 

 The fibular facet is comparatively smaller than in the llama. This is 

 especially true of that portion anterior to the groove which divides 

 this facet. In the type of O. lougipes the external astragalar facet has 

 a pit which is comparatively smaller than that of the camel. 



The Fibula. — The fibula, as in modern representatives of the 

 Canielidce, is reduced to the malleolus which articulates with the tibia, 

 astragalus and calcaneum. The rudimentary process of the shaft 

 is proportionally heavier than in the recent genera. It is trian- 

 gular in cross-section, terminates in a sharp point superiorly, and fits 

 closely into the deep groove on the external face of the tibia. 



The Tarsus. — The tarsus of Oxydactylus lougipes, as compared 

 with that of the camel and llama, is higher and much narrower, as 

 would be expected from the lighter structure of the entire limb already 

 noticed. The calcaneum is much longer, but of less diameter antero- 

 posteriorly than is that of the llama. The free truncated end of the 

 tuber shows characters similar to those of the recent genera. The 

 fibular facet is less prominent and is placed at a greater oblicjuity to 



