South. Dakota School of Mines 117 



Among the Miocene forms Procamelus has long been 

 known. This genus is of interest in that the camels and llamas 

 of today seem to have descended directly from it. Within the 

 Black Hills region its remains have not been found in quantity 

 and the much later studied genera Stenomylus and Oxydactylus 

 have received fuller description.* Specimens of these latter have 

 been found especially in northwestern Nebraska. A reproduc- 

 tion of the skeleton of Oxydactylus longipes as restored by 

 Peterson is given on Plate 49. Loomis describes Stenomylus 

 hitchcocki in Vol. 29, 19 10, of the American Journal of Science 

 more than forty skeletons of which were found in one excava- 

 tion five miles southeast of Agate Springs. In general it may be 

 said that the Miocene forms became increasingly more cameloid 

 in that they are larger, the side toes disappear, the metatarsal 

 bones become more fully united and rugosities of the hoof bones 

 indicate the presence of a small foot pad. 



With the close of the Miocene important geographical 

 changes came about including the raising of the isthmus of 

 Panama above sea level and the forming of a land connection 

 across Behring Strait. In this way widespread migration 

 became possible. The camels during and immediately subsequent 

 10 the developement of these land bridges were especially 

 abundant and diversified throughout North America., hence 

 readily took advantage of the opportunity to enter South 

 America in the one direction and Asia and thence to Europe 

 and Africa in the other. Later during Pliestocene time by 

 reason of unfavorable climate or other conditions the North 

 American branches of the family all died out while some at 

 least of the more favorably situated foreign members lived on. 

 Thus in the light of their ancestral history the wide separation 

 of such nearly related animals as the camel and the llama, so 

 long a perplexing question, is readily understood"'" 



CERVIDAE 



Until 1904 nothing was known of the ancestral deer within 



*Peterson, O. A. Osteology of Oxydactylus. Ann. Carnegie 

 Mus., Vol. 2, 1904, <pp. 434-476. 12 pis. 



Loomis, F. B. Osteology and Affinities of the Genus Stenomylus. 

 Am. Journ. Sci. Vol. 2 9, 1910, pp. 2 97-32 3. 



tin addition to the papers already mentioned the following gen- 

 eral review of extinct camels published some years ago will be found 

 of much value: Wortman, J. L. The Extinct Camelidae of North 

 America and Some Associated Forms. Bull. Am. iMus. Xat. Hist. Vol. 

 10, 1898, pp. 93-142. 



