92 EXTINCT MONSTERS 



Before we leave the skull there is one other very interesting 

 point that should not be omitted. If the reader will refer to the 

 skull of Mastodonsaurus (Fig. 16), he will see, just on the middle 

 line and near the base, a small round hole. It lies over the 

 brain-cavity, and most probably represents the site of a small 

 third eye. Whether this little extra eye was capable of receiving 

 impressions of light, and so of communicating them to the brain 



FIG. 16. Skull of a Labyrinthodont Mastodonsaurus Jaegeri, from New Bed 

 Sandstone, Germany. 



as an ordinary eye does, is a matter of doubt ; but in a certain 

 very primitive little lizard now living in New Zealand, and 

 known as the Tuatara (Sphenodon), there is a similar aperture 

 overlying the rudiment of an eye now quite useless and lying 

 down in the brain. This little eye in the Tuatara must at 

 one time have been made use of, and the question arises 

 whether the third eye of the Labyrinthodonts was similarly 



