256 EXTINCT MONSTERS 



these elevations, or horn-cores, has, of course, been preserved ; yet 

 a fortunate discovery may perhaps reveal their nature by the 

 form of a natural cast, as the eyeball of the Oreodon is sometimes 

 thus clearly indicated in the fine Miocene matrix which envelops 

 these animals." It looks rather as if we have here an early stage 

 in the evolution of horns, and it may be that in the course of 

 subsequent ages such prominences as those developed into true 

 " horn cores," such as sheep or goats have, while the thick bosses 

 of skin that covered them slowly developed into the true horns 

 that are attached to these cores. If this is so, then we have here 

 another instance of a " generalised " structure. Again, the limbs 

 with their five toes tell us at once that the creature's place in 

 Nature is outside of those two great groups of modern ungulates, 

 or hoofed quadrupeds, the odd-toed and the even-toed, represented 

 on the one hand by the horse, rhinoceros, and tapir, on the other 

 by the pig, camel, deer, ox, and many other forms. Probably the 

 two groups had not at this early period branched off from the 

 primitive ungulate stock with five toes in each foot, of which 

 the elephant is a living descendant, and from which also the 

 Dinoceras must have come. 



The limbs were strong and massive, but the brain was 

 remarkably small, so that our Dinoceras cannot be credited with 

 any high degree of intelligence : and here again we see an 

 absence of " specialisation " compared with the sagacious elephant. 

 Professor Marsh has taken casts of its brain-cavity (see Fig. 96). 

 These casts show that the brain was smaller (in proportion to 

 the size of the animal) than in any other mammal, whether living 

 or extinct and even less than in some reptiles ! In fact, it was 

 a decidedly reptilian kind of brain. Perhaps it may seem hardly 

 credible, but so small was the brain of Dinoceras mirabile, that 

 it could have been pulled through the apertures (neural canal) 



