^8o STRUCTURE OF VERTEBRATES 



genus Prolacerta shows how the lower vacuity may have been 

 lost ; it had a very small quadrat ojugal and a thin tapering jugal 

 which nearly reached the quadrate and may have been joined to 

 it by a ligament. 



.pTTl. 



^^'pCLTT 



— - sq. 



Fig. 453. — Skulls of reptiles. 



A, Dorsal view of the skull of the tuatara (Sphenodon) ; B, the same view of the skull of the grass snake 

 (Natrix natrix), with small portions of the lower jaw ; C, dorsal, and C, ventral views of the 

 skull of a crocodile. 



a.n.. Anterior nares ; a.pv., anterior palatine vacuity ; b.oc, basioccipital ; E.t., common opening of 

 Eustachian tubes ; epipt., epipterygoid ; ex.oc, exoccipital ; f.m., foramen magnum ; fr., frontal ; 

 ju., jugal; Ij., portion of lower jaw; l.t.f., lateral temporal fossa; lac, lacrimal; m.x., maxilla; 

 n., nasal ; n.i., notch into which fits the fourth tooth of the lower jaw ; o.i., opening into which fits 

 the first tooth of the lower jaw ; o.c, occipital condyle ; orb., orbit ; p.n., posterior nares ; p.p.v., 

 posterior palatine vacuity ;^a>'., parietal; ^/..palatine ;^;».,premaxilla ;/jr/., prefrontal ;^ro., pro-otic; 

 pt., pterygoid; ptf., post-frontal; pto., postorbital ; q., quadrate; q.j., quadratojugal ; s.oc, supra- 

 occipital ; sq., squamosal ; st.f., supratemporal foramen ; tpl., transpalatine. 



For the lizard and turtle, see Figs. 454 and 450. 



Note that the tuatara and crocodiles have both supratemporal and lateral temporal fossae, the lizard, 

 being without quadratojugal, has no lateral temporal fossa, the snake has neither arcade, and in the 

 turtle there are no fossae. 



