198 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



cipital processes in dinosaur skulls. Moreover the enlarged supraoccipital plate lies imme- 

 diately above this newly annexed region. The under side of the skull also exhibits a high 

 degree of specialization, as shown in Fig. 80C 



The otoliths of the siluroid fishes have yielded to Mr. G. Allan Frost (I925(:, p. 445) 

 the following significant conclusion: 



'rn.efh 



■sbrsfg 



Plecostomus commersonii 



Fig. 80. Plfcojtomus. A. Side view. B. Top view. C. Underside. 



