SOUTH DAKOTA SCHOOL OF MINES 



135 



Within the area described in this book, a number of 

 ancestral species have been identified, some from the Oligo- 

 cene and some from the Miocene. These are preceded else- 

 where by still older forms, the oldest of all so far as yet 

 known being Protylopus petersoni a little four toed creature 

 scarcely larger than a jackrabbit, found a few years ago in 

 the Upper Eocene beds of the Washaki basin, Wyoming, and 



Auclienia 

 South America 



Pllauchenia 



Extinct 



(Giraffe-camels) 



Alticamelus 



Procamelus 



Extinct 



Proto'meryx (Gazelle-camel) 

 Stenomylus 



Figure 70 — Phylogeny of the Camels. R. S. Lull; Organic Evolution, 

 1917. Published by the Macmillan Company. Reprinted by 

 permission. 



described by Mr. W. B. Matthew of the American Museum 

 of Natural History. 



The best known South Dakota species, the one first dis- 

 covered, and the one that has received the most merited 

 recognition is Poebroth er ium icilsoni. (Plate 46). The col- 

 lection of Big Badland material given by Mr. Alexander Cul- 



