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STUDIES FOR STUDENTS 



forms have the enamel entirely removed from the tops of the 

 tubercles and the spaces between the walls filled up with a softer 

 and more rapidly wearing cement. 



Three general divisions may be recognized, the antelopes, the 

 sheep and the bovine tribe. The oldest of these, the antelopes, 

 appeared in the Miocene of Europe and southern India.' They 

 seem to be derived directly from the Cervulinae ', a subfamily of 

 the Cervicornia represented by Dremotherium and Amphitragidus . 

 During the Pliocene the three groups were differentiated. 



PI 



ocene. 



Antilopinae. Ovinoe. Bovinae. 



Upper 

 1 ocene. 



Antilopinae. 



Lower 

 v/liocene. 



Cervulinae. 

 Dremotherium and Amphitraoulus. 



Proboscidea. — The origin of this suborder is not at all well 

 understood, the first members of the group are found in the 

 Miocene time and in all the essential characters are as well 

 developed as the most advanced of the living forms. In many 

 of their characters the Proboscidea are very primitive ; the struc- 

 ture of the feet- and of the carpus and tarsus, the structure of the 

 limbs and other parts of the body, are such as are found in the 

 earliest ungulates. The development of the proboscis and the 

 correl'ated shortening of the neck and the development of the 

 peculiar dentition are the only characters that define the group. 

 The most characteristic feature is the development of the incisor 

 teeth as tusks which in some forms occur in both the upper and 

 the lower jaws, in others in the lower jaws, and in the most mod- 

 ern forms in the upper jaws. In the earliest forms there were 

 many teeth in the jaws, each one with strong transverse ridges 

 completely covered with enamel ; in the advance of the group 

 the ridges on the teeth seemed to multiply until they became 

 very numerous, and at the same time the enamel disappeared 



