SOUTH DAKOTA SCHOOL OF MINES 



107 



flexed on each other than would seem justifiable, judging 

 from recent animals. Scott states that the obliquity of the 

 faces of the dorsal and lumbar vertebrae show that the back 

 was decidedly arched. 



The skull was about seven inches in length. The brain 

 was large and apparently well convoluted. It weighed about 

 one-third as much as the brain of the average present day 

 horse. The number of teeth was forty-four, the arrangement 

 on each side, above and below, as follows: Incisors, three; 



PlioKippus "lulliamis 



Figure 46 — Skull of the earliest known one-toed horse Pliohippus 

 lullianus. (A colt ten months old.) Named by Troxell and 

 found near Mission, on the Rosebud Indian Reservation, South 

 Dakota in beds of probably Lower Pliocene age. Osborn, 1918. 



