No. i.] OSTEOLOGY OF PCEBROTHERIUM. 69 



is not so deep, nor does it divide the fibular facets into two 

 parts, as in the recent genera. 



The tarsus is high and narrow. The calcaneum is long and 

 slender, the astragalus high ; the cuboid is likewise high and 

 narrow, and the calcaneal facet deeply incised and broader than 

 the astragalar ; the latter and the astragalar facet of the navicu- 

 lar are emarginated by a median but shallow and small fossa. 

 The ecto- and meso-cuneiforms are co-ossified. 



The median metatarsals are longer and stouter than the 

 metacarpals, the increased diameter being the antero-posterior 

 rather than the transverse, and the posterior hooks are very 

 long and stout. Mts. II and V are small scale-like rudiments ; 

 the former sometimes, but not always anchylosed with No. Ill, 

 the latter always free. 



Of the hind limb of Procamelns (PI. Ill, Fig. 53) I have the 

 distal end of the tibia, proximal end of the cannon-bone, the cal- 

 caneum, astragalus, and navicular of a large species from the 

 Loup Fork of Oregon, and Cope has figured the cuboid. Judg- 

 ing from these remains, it would appear that the hind limb of 

 this genus has very nearly reached the modern condition. The 

 distal end of the tibia is broad and heavy ; the malleolus is 

 shorter and more massive than in PcebrotJierium ; the intercon- 

 dylar ridge, lower and broader, and its articular surface is inter- 

 rupted by a deep fossa. The groove for the fibula is very deep, 

 and separates the fibular facet into a smaller anterior and larger 

 posterior portion. 



The astragalus has become much broader in proportion to its 

 height, and the rim of the external condyle much thicker. The 

 calcaneum is compressed and deep, with prominent sustentacu- 

 lum and long narrow cuboidal facet. On the inner side of the 

 distal end can be seen the beginning of the projection which in 

 the llama extends far inwards behind the astragalus ; the distal 

 end extends little if any below that of the astragalus. The navic- 

 ular is very low ; the fossa, which in PcebrotJierium emarginates 

 the fibular edge of the astragalar surface, is here larger and 

 deeper. The cuboid is also very low vertically ; the calcaneal 

 facet is but little incised. 



The upper end of the cannon-bone is heavy and deep antero- 

 posteriorly. The posterior hook-like projections are relatively 

 shorter but more massive than in Pcebrothcrinm. The prox- 



