268 



HISTORICAL GEOLOGY 



in the rear. All were plant-eaters. The brains of all Dinosaurs 

 were almost incredibly small, even as compared with modern 

 Reptiles, and "this was especially true of Stegosaurs. To make up 

 for this deficiency they had an enormous enlargement of the 

 spinal cord in the sacral region (i.e. over the hind legs). This 

 sacral brain — if we may so call it — was ten to twenty times 



Fig. 168 

 The hugest of all known Dinosaurs, a Sauropod, Diplodocus. A mounted 

 skeleton in the Carnegie Museum of Pittsburg measures 87 feet long. 

 Restored by C. R. Knight under the direction of H. F. Osborn. (Courtesy 

 of the American Museum of Natural History.) 



bigger than the cranial brain. It was necessary in order to work 

 the powerful hind-legs and tail" (J. LeConte). Stegosaurs existed 

 through all of the Mesozoic except the Triassic. 



Triceratops was another strange-looking creature, so named 

 because of its three horns — two of great size just back of the eyes 

 and a smaller one on the nose (see Fig. 170). The enormous 

 flattened skull had a sharp beak in front. The skull extended 

 backward into an immense hood or cape-like structure. According 

 to Marsh they (Triceratops) had the largest heads and smallest 

 brains of the Reptiles, and hence they must have been exceedingly 

 stupid. Skulls 6 or 8 feet long have been found. The four legs 



