PLATE 46. 



CENTRACIONTIDAE. 



Fig. 1-6. Centh.^cion francisci (Page 186). 



1. Jaws of a specimen of medium size. 



2. Upper jaws and teeth of the same. 



3. Lower jaws and teeth of the same. 



4. Jaws of an old individual. 



5. Upper jaws and teeth of the same. 



6. Lower jaws and teeth of the same. 



These figures are from older specimens than those shown on Plate 45. Tliey indicate the decided 

 change that takes place in the feeding habits. The hinder teeth are all molars, with a low ridge instead 

 of cusps, and are much wider and more swollen than the front teeth, some of the hindmost of which 

 apparently have been succeeded, when renewed, by molars in their particular rows. 



