TDE NERVES AND BRAIN 



135 



many times more nerve-matter. It was a sort of sec- 

 ond or lower brain. Here is Professor Marsh's resto- 

 ration of one of these— the Stegosaurus — with shell - 

 plates set on edge. Look at the small skull. The 

 brain was quite likely used only for the senses of 



Fig. Q2.Ste<josaurus ungulatus (after Marsh), >= bV, Jurassic, 

 Wyoming. 



sight, smell, etc., and it is not unlikely that it Avould 

 have been dangerous to come within reach of that 

 terrible spiny tail months after the head was cut off 

 (Fig. 62). 



We can not note the parts of the brain except to 

 say that a certain little gland found on the top of that 

 of mammals is ol)served to be much larger in most 

 reptiles, and it was once, doubtless, in some, an active 

 third optic lobe corresponding to a useful third eye. 

 11 



