136 THE WHITE RIVER BADLANDS 



bertson in 1847 to the Academy of Natural Sciences of Phil- 

 adelphia contained a broken skull of this animal and Dr. 

 Leidy in describing the specimen, the first of the many South 

 Dakota badland fossible vertebrates studied by him, gave it 

 the name it bears. (See Figure 2). He first regarded the 

 animal as allied to the musk deer but later indicated its 

 cameloid nature. Since the description of this earliest 

 Poebrotherium skull abundant other remains have been 

 found but generally they have not been complete. In 1890 

 the Princeton expedition was fortunate in securing a very 

 excellent skeleton of Poebrotherium wilsoni almost entire 

 and Prof. Scott has described this in a most careful man- 

 ner. It is not possible, nor would it be profitable to go into 

 the details of this description here. Briefly it may be said 

 that the animal was a lightly built, graceful creature with 

 apparently some external likeness to the llama but of about 

 the size and build of the existing gazelle. It shows its 

 relationship in many features of its skeleton but as in many 

 extinct animals the bones show a primitive or generalized 

 nature, and its connection with the llamas is perhaps as 

 close as with the true camels. The eyes are farther back 

 than in the present day camel, the ribs are more slender, 

 and the foot, armed with small pointed hoofs was 

 apparently without a pad. Like the existing camel 

 the foot has only two toes, the third and fourth, but 

 traces of the second and fifth remain as evidenced by the 

 metapodial nodules. The metatarsal bones are separate but 

 pressed closely together and plainly anticipate the definite 

 union into a "cannon bone" during the subsequent Miocene. 

 The animals varied considerably in size, the larger indi- 

 viduals reaching a height of twenty-four inches. 



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. 

 The gazelle camel, Stenomylus, and the giraffe camel, Oxy- 

 dactylus, were discovered later but they have received full 

 description. Their remains have been found in particular 

 abundance in northwestern Nebraska. Several dozen skele- 

 tons of Stenomylus, were obtained from one excavation near 

 Agate Springs. Peterson says it is seldom that the complete 

 knowledge of the osteology of a genus has been acquired so 

 rapidly after its discovery as that of Stenomylus and that 



