SOUTH DAKOTA SCHOOL OF MINES 129 



The first Protoceras specimen was obtained by Mr. J. 

 B. Hatcher in 1890. It, like all subsequent material of this 

 kind, was found near the highest part of the Big Badlands, 

 where the Protoceras beds are well exposed. In January, 

 1891, Prof. Marsh described the animal in the American 

 Journal of Science under the name Protoceras celer in al- 

 lusion to the early appearance of horns in this fleet-footed 

 group of artiodactyls. Before this discovery no horned 

 artiodactyls were known to have lived earlier than Pliocene 

 time. Marsh states it as an important fact that while all 

 existing mammals with horns in pairs are artiodactyls and 

 none of the recent perissodactyls are thus provided, the re- 

 verse of this was true among the early forms of these 

 groups. 



The head is especially unique. ( Plate 23 ) . It displays 

 in many ways the modernized type of structure, and shows 



Figure 65 — Skeleton of the Oligocene ruminant, Leptomeryx evansi. 

 Scott, 1891. 



sexual differences unparalleled among the ancient artio- 

 dactyls. The most obvious characters are the bony protu- 

 berances from various parts of the head in the male. 

 In the female these are only faintly indicated. In the 

 male a pair of protuberances project upwards from the 

 rear part of the head in much the same position as the 

 horns of the present day pronghorn antelope. Near the 

 anterior end of the face there is a second pair, laterally 

 compressed and more prominent than the first pair. Over 



