572 



REPTILES. 



The ribs are numerous, but only five reach the sternum. 



The skull is well ossified, but in the region of the nares, 

 in the interorbital septum, &c., the primitive cartilaginous 

 brain-box persists. On the dorsal surface the bones exhibit 

 numerous impressions made by the epidermic scales, which 

 render it difficult to distinguish the true sutures of the 

 bones. 



Two fused parietals with the rounded median " parietal foramen," two 

 frontals, and the two nasals, are the most important constituents of the 

 roof of the skull. Anteriorly the premaxillse appear between the nasals, 

 while posteriorly the sickle-shaped squamosal is attached by a suture to 

 the parietal, and is overlapped by one of the two small supra-temporal 



Fig. 196.— Side view of skull of Lacerta. (After W. K. Parker.) 



px.^ Premaxilla; e.n., e.\lemal nostril; jnx., ma-\illa ; /., lach- 

 rymal ; /, jugal ; II., oplic nerve ; t.pa., trans-palatine ; cp.g,, epi- 

 pterygoid ; pg., pterygoid ; I'.pg., basi-pterygoid ; t.o. , basi-occipital ; 

 ^., quadrate; oc.c, occipital condyle; s^., squamosal ; pr.i>., pro-otic; 

 pt.o., post-orbital ; sii. st2.^ supra-temporals ; ps., presphenoid ; p.c, 

 mesethmoid ; s.o.^., supra-orbitals ; i.o.n., inter-orbital notch;//;, 

 prefrontal ; w. , nasal ; oj.^ olfactory sac ; ar.^ articular ; ag., angu- 

 lar ; sag.^ surangular ; cr., coronary ; d., dentary. 



bones. The orbit is roofed by a series of small bones, of which the 

 anterior and posterior are respectively known as pre- and post-frontal. 



On the floor of the adult skull there is a large basal bone, composed 

 of fused occipital and sphenoidal elements, anil continued forward as a 

 slender bar (parasphenoid). This bone gives oft two stout processes, 

 the basipterygoid processes, which articulate with tlie pterygoids. Each 

 [ilerygoid is connected posteriorly to the quadrate bone of the corre- 

 sponding side, and anteriorly with the palatine. From the union of 



