no Bulletin American Museum of Natural History. [Vol. X^ 



ance of the later Camels, but on the contrary, are more or less 

 triangular upon cross section, especially in the proximal half of 

 their shafts. The metapodials as well as the long bones show 

 their cameloid affinities in the unusually large size of the medul- 

 lary cavities. The phalanges exhibit comparatively few differ- 

 ences from those of Poebrotherium, the unguals being flattened 

 upon their opposed surfaces. The fore foot is entirely unknown, 

 but it is highly probable that it will be found to possess four 

 complete functional toes. 



It may transpire that the association of this skeleton with the 

 above-described skull is incorrect, and that these bones belong to 

 separate and distinct species; however, they agree so well in the 

 matter of proportionate sizes of the different parts, and both are 

 so distinctly cameloid, that I am persuaded to believe that they 

 refer to one and the same species. It may be noted here, how- 

 ever, that in one of the specimens referred to above (No. 2067), 

 there is evidence that at least one of the lateral metapodials of 

 the hind foot was complete though very slender, and should prob- 

 ably be referred to another species on this account. The bones 

 are, moreover, somewhat more slender and delicate than the one 

 here described. At all events, whatever form of skull belongs 

 with these skeletal parts it is nevertheless certain that the skull of 

 Protylopus, above described, is just such a type as is required to 

 satisfy all the necessary conditions in order to occupy a position 

 in direct ancestral relation with Poebrotherium. The true Tylo- 

 pod phylum is therefore traceable directly to it. Beyond this, 

 there is at present no satisfactory evidence to establish, with any 

 degree of certainty, the identity of the true Camel pedigree. 



Poebrotherium I.eidy. 



With a consideration of this genus we pass from the Eocene 

 to the Oligocene representatives of the group. It was estab- 

 lished by Leidy as early as 1847 upon an imperfect skull presen- 

 ted to the Philadelphia Academy by Mr. Alexander Culbertson 

 of Chambersburg, Pa., who was at the time engaged in the 

 western fur trade. It was among the first of the mammalian 

 fossils from the remarkable Bad Lands of the Cheyenne River 



