290 FOSSIL REPTILES. 



They are, however, continued under the palatines in a con- 

 cavity of their surface. These two bones are less separated 

 from each other. 



In the pterygoidean bones, that part which is between the 

 apophysis of the sphenoid and the tympanic bone is hollowed 

 into a canal, deeper at its lower or internal face. The tym- 

 panic bone is widened at the summit, and slightly concave 

 externally. 



The basilary has on each side a descending tubercle, which 

 is wanting in the ouaran. The lamina which separates the 

 pituitary foss from that of the cerebrum is less prominent. 



The osselets, representing the alae temporales^ are in the 

 form of a Y, the two upper branches of which end at the 

 frontal and parietal, and the inferior at the sphenoid, at the 

 place where it comes forward in the form of a crest, or ridge, 

 to serve as a basis to the interorbital partition. 



In this same partition are also certain ossified parts, repre- 

 senting the orbital wing, and distributed so as to leave a 

 foramen common to this interorbital partition, and to that of 

 the cerebrum. Into this foramen pass the optic nerves, before 

 the two temporal wings of which we have spoken. Behind 

 them, but in front of the point opposite to which is the colu^ 

 mella, pass the nerves of the third, fourth, and sixth pair, and 

 the nerve of Willis ; and behind this columella, into an emar- 

 gination of the os petrosum, passes the rest of the fifth pair. 

 Thus this emarginated division corresponds with the fenestra 

 rotunda and the fenestra ovalis. 



The Dracaena of Lacepede, not Linnaeus, resembles almost 

 in every thing the last-mentioned species. The resemblance 

 also is still stronger in the bicarinata and the ameiva. 



The lizards, properly so called, such as the lacerta agilisy 

 independently of some details of forms and proportions, have 

 all the characters of the last, except what follow : — The 

 principal frontal is longitudinally divided into two bones. 

 The anterior frontal descends but little into the orbit, where 



