64 THE GEOLOGICAL EVIDENCES 



In following back the ancestral line of these 

 hornless ruminants we can detect a series of 

 very remarkable and gradual modifications which 

 connect the modern animal with animal forms 

 very unlike itself. Thus, in one of the earliest 

 members of the cameline series, the Oligocene 

 or Miocene Poebrotherium, whose species appear 

 to have had the slender and graceful proportions 

 of the modern gazelles, the metapodial bones 

 were distinct, and the mouth was furnished with a 

 complete series of incisor teeth. This distinguish- 

 ing dental character is retained in the succeed- 

 ing Protolabis (Middle Miocene), but whether or 

 not the metapodials were united into a single 

 cannon-bone is still unknown. In the Upper Mio- 

 cene Procamelus, whose forms ranged in size 

 intermediate between the sheep and camel, the 

 incisor teeth have been reduced to the normal 

 number found in the camels, although the pre- 

 molars still conform to the formula |, instead of 

 f, which distinguishes the genus Camelus. An 

 intermediate position between Procamelus and 



