SKULL — REPTILES 



157 



and premaxillce are fused in the same way and the nasals are united to the 

 premaxillce. They have a parietal foramen. The exoccipitals have strong 

 parotic processes, possibly otoccipital. Vomers and palatines of the two sides 

 are distinct, but the latter touch in the middle line. The mobile quadrate, 

 articulated dorsally to the squamosal, is either notched or perforate for the 

 columella, recalling the Chelonia. The orbit (containing sclerotic bones) is 

 closed behind by an arcade formed by zygomatic and (apparently) fused post- 

 orbital and postfrontal bones, a posterior process of which meets the squamosal 

 to form the temporal arcade. The transversum is small and connects only 



Fig. 167. — Dorsal, ventral and side views of skull of Clidasles velox (Williston, '98). 

 ar, articulare; bo, basioccipital; c, coronoid; d, dentale;/, frontal; /, lacrimal; w, maxilla; 

 n, naris; p, petrosal; pa, parietal; pf, postfrontal; pi, palatine; ./>?«, premaxilla; po, 

 postfrontal; prf, prefrontal; pi, pterygoid; q, quadrate; sp, splenial; sq, squamosal; 

 V, vomer; s, zygomatic. 



pterygoid and zygomatic, the latter extending so far forwards as to exclude the 

 maxilla. There are fewer bones in the lower jaw than in embryo lizards and a 

 peculiarity is that between dentary and splenial in front, and coronoid, angulare 

 and .surangulare behind, there is a hinge which permitted a wide separation of the 

 anterior parts of the jaw, this freedom apparently being increased by a hgament, 

 as in snakes, between the tips of the two halves of the jaw. 



