128 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



out by the enlarged metapterygoid. In short the preopercular of Lepidosteus, while 

 retaining its normal relations lateral to the hyomandibular and symplectic has expanded 

 on its posterior and inferior borders, and has lost its contact with the forwardly shifted 

 quadrate. Meanwhile the interopercular, retaining its ligamentary connection with the 

 derm-angular, has moved forward, losing its normal connection with the subopercular and 

 usurping the position of the preopercular as the lateral brace of the quadrate. 



/ , "at*." 

 (antorb}- 



"n?" /detfi 



KK^ti 



Fig. 23. Comparison of Lepidosteus and Amia skulls. Top view. 

 A. Lepidosteus tristoechus. B. Amia calva. 



The long bones on the dorsal surface of the anterior part of the snout are regarded as 

 homologous with the ascending processes of the premaxillae of Amia, as shown by Tate 

 Regan. * Mayhew calls them nasopremaxillaries. The small ethmoid appears to represent 

 the rostral or postrostral of palasoniscids, and the mesethmoid (dermethmoid) of teleosts. 

 The nasal and adnasal together retain the relations of the antorbital of palsoniscids except 

 that by the elongation of the snout they are far removed from the eye. The lacrymal has 



