HISTORY OF THE PROBOSCIDEA 435 



that the early tendency toward a considerable cerebral devel- 

 opment shown in these primitive Proboscidea is one of the 

 causes why the group has survived and flourished through so 

 long a period " (Andrews). The cranium was very long and 

 the facial region extremely short, the premaxillaries not being 

 prolonged into a snout, as they were in "{Paloeomastodon ; the 

 occipital bones formed nearly the entire posterior surface of 

 the cranium and even encroached slightly upon the roof. There 

 was a long, but not very prominent, sagittal crest, and some of 

 the cranial bones were much thickened ; in one species the 

 hinder part of the cranial walls was distinctly inflated, a begin- 

 ning of the enormous thickening which has culminated in the 

 true elephants. The nasal bones were already much shortened, 

 though they were twice as long as those of fPakeotnasto- 

 don, and the animal would appear to have had an incipient 

 proboscis. 



The neck was of moderate length and the body very long, 

 with at least twenty pairs of ribs, and there was probably 

 a long tail. The hip-bone differed remarkably in its extreme 

 narrowness from that of the later Proboscidea and the limb- 

 bones were much more slender, though not dissimilar in shape. 



At a very early period the order became divided into two 

 main branches, one of which includes all the forms so far 

 considered, and the other the very strange ]Diriotherium. The 

 fdinotheres entered Europe together with the fmastodons 

 in the lower Miocene and continued into the Pliocene without 

 much change and then died out, leaving no descendants. 

 They never invaded North America, probably because they 

 were of more or less aquatic habit, like the hippopotamuses, 

 and therefore less likely to find suitable conditions in the 

 narrow and unstable land-bridges which connected the Old 

 World with the New, than were animals of purely terrestrial 

 habitat. The fdinotheres were of huge size, equalling the 

 larger elephants in this respect and closely resembling them in 

 the skeleton of the body and limbs. As usual in this order. 



