FIG. 54. Diagrams of skulls, showing especially the composition of the bony arches of 

 the orbito-temporal region. 



A, C, D, E, THEROMORPHA. A, Elginia, p. 305 ; C, Cynognathus. p. 306 : D, 

 Vordonia, p. 310 ; E, Dicynodon, p. 310. 



B, G, PROSAURIA. B, Sphenodon, p. 294 ; G, Palaeohatteria, p. 291 . 

 F, CROCODILIA, p. 434. 



H, I, K, CHELONIA, p. 316. H, Chelydra, p. 338 ; I, Chrysemys, p. 346 ; K, 

 Cistudo, p. 361. 



E, Epiotic ; F, frontal ; IT, infratemporal fossa ; J, jugal, shaded vertically ; 

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

 P, parietal ; Po, postorbital, dotted ; Pf, post-frontal ; Pm, premaxillary ; 

 Pr, prefrontal ; Ptg, pterygoid ; ^quadrate; (tf, quadrato-jugal ; So, supra- 

 occipital ; Sq, squamosal, shaded obliquely ; St (in B-E), suprateniporal fossa ; 

 St (in A), Supratemporal bone. 



