REPTILES. 



323 



are fused with the exoccipital, and the basi- and presphenoids are united. 

 Post- and prefrontals and lachrymals are present, and the vomers are 

 paired. There is an os transversum, but jugals and quadratojugals are 



FIG. 317. Diagram of the cephalic plates in a colubrine snake, f, frenal; ft, 

 frontal; i, internasal ; ?7, infralabial ; n, nasal; /, parietal; pf, prefrontal; po, 

 postorbital ; pro, preorbital ; r, rostral; si, supralabial. 



lacking. The premaxillary is very small, and there is no columella. The 

 quadrate is articulated to the supratemporal (squamosal auct], which in 

 most forms has but a loose connection wjth the other bones of the skull. 

 Teeth occur on the maxillae and pterygoids, and usually on the palatines, 



FIG. 318. Skull of garter-snake (Eutainia sirtalis}. a, angulare ; d, dentary ; 

 e, ethmoid; /, frontal; ///, maxillary; n, nasal; /, parietal; pa, palatine; pm, 

 premaxillary; pf, prefrontal ; po, postfrontal ; ps, parasphenoid ; //, pterygoid; q, 

 quadrate ; s, sypratemporal ; /, transversum ; v, vomer. 



and they may be present on premaxilla. The teeth are usually sharp, 

 conic, and retrorse, and frequently those of the maxilla may be grooved. 

 When the grooved teeth occur on the anterior end of the maxilla (Protero- 

 glypha, Solenoglypha) they are connected with poison glands. The rami 



