MAMMALIA. 



323 



important links for uniting in a natural series the several 

 groups of which it is composed. Their toes are enveloped 

 in horny hoofs ; they are all herbivorous ; most of the 

 genera are remarkable for the thickness of their skin, which 

 gives value to the name Pachyderm. "We divide it into three 



.-- 



FIG. 225. Auchenia glama. 



families the solid-hoofed, the ordinary pachyderms, and 

 the proboscidians. 



FIG. 226. Skull of the horse. 



1st Family. The SOLIPED.&. The extremities have a 

 single toe to each foot. The dental formula is, incisors, , 



* 2 



