Qj ' 



Fig. 55. — Diagrams of skulls, showing especially the composition of the bony arches of 

 the orbito-temporal region. 



L, Pythonomokpha. Clidastes, p. 490. 



M, N, 0, Lacertilia, p. 496. M, Varanus, p. 543 ; N, Uromastix, p. S24 ; O, 



Lacerta, p. 550. 

 P, ICHTHTOSAURIA, p. 479. Ichthyosaurus, p. 483. 

 Q, Pterosaueia, p. 484. Dimorphodon, p. 486. 

 R, AvES, generalised, for comparison. 

 S, Mammalia, generalised, for comparison. 

 T, Ophidia, p. 581. 



O, Condyle of mandible ; Col, columella cranii ; F, frontal ; /, interparietal or 

 pineal foramen ; l.A, Inner angle of mandible ; J, jugal, shaded vertically ; 

 L, lacrymal ; M, maxillary ; N, nasal groove ; Na, nasal bone ; 0, orbit ; 

 Oj, preorbital fossa ; P, parietal ; Pf, postfrontal ; Pm, premaxillary ; Pr, pre- 

 frontal ; Ptg, pterygoid ; Q, quadrate ; Qj, quadrato - jugal ; .S^, squamosal, 

 shaded obliquely ; St, supratemporal bone. 



