SKULL — REPTILES 



163 



phals and to the Cotylosaurs, has but the lower fossa, while the wide separation 

 of postorbital and postfrontal suggest that the upper fossa is merged with the 

 orbit. This genus has a large parietal foramen, an epipterygoid and a vacuity 

 lateral to either pterygoid, and an interpterygoid space. Sclerotics are present, 

 while the posterior lateral angle of the cranium is formed by a so-called epiotic 

 (tabulare). 



The Thalattosauria are extinct aquatic reptiles with Rhynchocephalian 

 affinities. The infratemporal fossa is the larger, the two being separated by 

 postfrontal and squamosal, the lower arcade consisting of zj'gomatic and 



possibly squamosal, a quadratojugal being 

 absent. The naris, near the orbit, is 

 bounded by frontal, nasal, maxilla and pre- 

 maxilla, the latter bone being long. Pari- 

 etals and frontals are paired; pre- and 

 postfrontal meet above the orbit, the rest 



Fig. 174- Fig. 175. 



Fig. 174. — Palatal surface of Sphenodon (McGregor, '06). bu, basioccipital; 

 bs, basisphenoid; eo, exoccipital; tn, ma.xilla; o, opisthotic; pi, palatine; po, postorbital; 

 ps, presphenoid; pt, pterygoid; q, quadrate; qj, quadratojugal; s, stapes; v, vomer; 

 z, zygomatic. 



Fig. 175. — Skull of Palaohatteria (Jaekel, '11). a, articulare; an, angulare; c, 

 coronoid; d, dentate; /, frontal; /, lacrimal; m, maxilla; p, parietal; pf, px)Stf rontal ; 

 pm, premaxilla; po, postorbital; prf, prefrontal; qj, quadratojugal; s, splenial; sa, 

 surangulare; sq, squamosal; s, zygomatic. 



of its border being formed by lacrimal and zygomatic, no postorbital occur- 

 ring. Sclerotics are present. The choanie, just ventral to the nares, are 

 bounded by maxillas and palatines, and it is uncertain whether the toothed vomer 

 is single or paired. What are called pterygoids are toothed, and apparently 

 an epipterygoid occurs. The long dentale is largely on the medial side of the 

 lower jaw, the angulare extending far forwards on the outer side. The articu- 

 lare also is long, its anterior end being covered by a large splenial; the coronoid 

 strong and the surangular large. 



CROCODILI.A.. — The chondrocranium (fig. 176) is more like that of lizards 

 than that of any other group. It lacks a basicranial fenestra, the posterior 

 tectum is nearly vertical, not horizontal as in lizards. The basipterygoid 

 processes are reduced, while the basitrabecular processes are large, as in birds. 



