136 ANIMAL LIFE PAST AND PRESENT. 



a length of over eight feet. No other known animals, 

 except whales, have a skull making any approach to 

 these dimensions ; that of the huge Atlantosaur being 

 very small in comparison with the bulk of its owner. 

 The skull before us is likewise remarkable for its 

 wedge-like form when viewed from above, and carries 

 a pair of large horn-cores immediately over the eyes, 

 and a short and single core above the nose. During 

 life it may be inferred with a high degree of proba- 

 bility that these bony cores were sheathed with horn, 

 like those of oxen, and that they proved equally 

 effective weapons of defence. 



The structure of the teeth is somewhat similar to 

 that obtaining in the Iguanodon, but each tooth has 

 two distinct roots. As in the latter, the extremity of 

 the lower jaw is devoid of teeth, and likewise has a 

 separate terminal bone. The upper jaw is, however, 

 peculiar in having a distinct toothless bone at the 

 extremity of the muzzle ; so that it would seem probable 

 that the mouth of these reptiles formed a kind of beak 

 sheathed in horn like that of a tortoise. In young 

 individuals the front horn-core is a separate bone, but 

 in the adult it became firmly united to the underlying 

 bones, so that in this respect we have a precise analogy 

 with the horn-cores of the giraffe. The brain of the 

 creature is very minute relatively smaller, indeed, than 

 in any known Vertebrate; this, however, might have been 

 expected from the diminutive size of the brain in other 

 Dinosaurs, since, in the same groups, large animals always 

 have relatively smaller brains than their smaller allies. 



