REPTILIAN SKULL. 



143 



FIG. 91. 



DIAGRAM OF THE CRANIAL EOOF IN A STEGOCEPHALIAN, VARIOUS TYPES OF 

 REPTILES, AND A BIRD, SHOWING MODIFICATIONS IN THE POSTEHO-LATEBAL 

 REGION. 



A. Stegocephalian (Mastodonsaurus giganteus, about one-fifteenth nat. size, 

 after E. Fraas). B. Generalized Anomodont or Sauropterygian, passing 

 with slight modification into the Chelonian (sutures dotted to denote in- 

 constancy in fusion of elements). C. Ichthyosaurus. D. Generalized Rhyu- 

 chocephalian, Dinosaurian, Crocodilian, or Ornithosaurian. E. Generalized 

 Lacertilian, often losing even the arcade here indicated. F. Generalized 

 Bird, fr., frontal ; j, jugal ; /, lateral temporal vacuity ; la., lachrymal ; 

 in.r., maxilla; n, narial opening; na., nasal; o, orbit; pa., parietal; 

 pnix., premaxilla ; prf., prefrontal ; ptf., postfrontal ; pto., postorbital ; 

 q.j., quadrato-jugal ; qu., quadrate; , supratemporal vacuity ; s.t. , supra- 

 temporals and prosquamosal ; sq., squamosal. Vacuities shaded with 

 vertical lines, cartilage bones dotted. 



