Insert on Page 88. 



UNGULATA. 



The order Ungulata (Herbivores) as now constituted in- 

 cludes the mammals once loosely classed as Ruminants, and 

 Pachyderms. The earliest known forms much resemble the 

 primitive Carnivores. The ancestors of both seem to have been 

 omnivorous. 



For some reason there appeared very early among the 

 Ungulates a tendency to develop the herbivorous type of tooth 

 and the digitigrade foot (walking upon the tips of the toes). 

 The change in the foot from the five toed plantigrade form pro- 

 gressed along two different lines and thus there were produced 

 two very different types, namely, the odd-toed type and the 

 even-toed type. In the odd-toed type the axis of the foot is in 

 the third or middle digit (mesaxonic). Animals of this type 

 are known as Perissodactyls. Their present day representatives 

 are the horse, the tapir, and the rhinoceros. In the even-toed 

 types, the axis of the foot is between the third and fourth digits 

 (paraxonic). Animals of this type are known as Artiodactyls. 

 Their present day representatives are the hog, hippopotamus, 

 chevrotain, camel, lama, deer, giraffe, antelope, ox, sheep, goat, 

 bison, et cetera. The Ungulates occurring in the badland forma- 

 tions of the Black Hills region are grouped as follows : 



Perissodactyls. Rhinocerotoidea, Lophiodontidae, Tap- 

 iridae, Equidae. Titanotheriidae. 



Artiodactyls, (page 103). Elotheriidae, Dicotylidae, 

 Leptochoeridae, Anthracotheriidae, Oreodontidae, Hypertraguli- 

 dae, Camelidae, Cervidae. 



