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THE POPULAR SCIENCE MONTHLY. 



stegosaurus, the remains of wliich have also been found in the 

 Western Jurassic and are preserved at the Yale College Museum. 

 It was about twenty-five feet long. Its skull contained a brain 



which is comparatively the 

 smallest brain which we know 

 in any quadruped. It was, 

 indeed, so small that it was 

 probably not sufficient to con- 

 trol and direct all the nerves 

 and muscles of the gigantic 

 body. At any rate, we find in 

 the stegosaurus that the ver- 

 tebrae of the sacrum contain a 

 cavity formed by an enlarge- 

 ment of the spinal canal. This 

 chamber is ovate in form, and 

 resembles the brain-case in 

 the skull, but it is very much 

 larger, being at least ten times 

 the size of the cavity of the 

 brain. Although we find in 

 some animals a swelling of 

 the spinal cord at the same 

 place, there is nothing known 

 which might be put beside the 

 stegosaurus in this respect, 

 and it is difficult to object 

 if somebody claims that the 

 animal possessed two brains 

 — one in his skull and the 

 other in his sacrum. The 

 stegosaurus was, according to 

 Marsh, protected and armed 

 in the following way : At the 

 region of the throat and low- 

 er part of the neck there were 

 small dermal plates in the 

 thick skin, which were regu- 

 larly arranged. The upper 

 part of the neck was shielded 

 by larger plates of the same 

 kind, which were placed in 

 pairs on each side. These 

 plates of bone increased in 

 size posteriorly, and covered 

 the back. From the sacrum 



