Class 4. Beptilla. 



415 



proportionsj just as does the cerebellum, wHioli in Lacertilia and 

 'Ophidia forms simply a narrow ridge in front of the medulla oblongata. 



Olfactory organs, the 

 nasal capsules, occupy the front 

 end of the head, and are sepa- 

 rated from one another by the 

 nasal septum. Each capsule is 

 a fairly roomy cavity, usually 

 provided with a large projecting 

 fold, the turbinal; the ex- 

 ternal nares are small, the 

 internal usually open far for- 

 wards in the mouth, and are 

 often prolonged into a groove 

 ■on the roof ; in Crocodiles, 

 however, this groove, by the 

 curving over and concrescence 

 'Of its edges, has become a tube, 

 •opening far back in the mouth 

 (Fig. 346), and covered below 

 by portions of the maxilla, 

 palatine, and pterygoid. 



Optic Organs. The 

 sclerotic is usually partly carti- 

 laginous, and in Lacertilia and 

 ■Chelonia, though not in Ophidia and Crocodilia, it exhibits a 

 ring of thin, bony plates, the sclerotic ring, surrounding the 

 cornea. In Lizards, a process, projecting freely into the vitreous 

 humour, and corresponding to the p e c t e n of Birds, arises from 



Fig. 343. Brain of a Lizard from above 

 (A) and from below (B). I olfactory lobes, 

 /cerebrum, mi optic lobes, b cerebellum, 

 e medulla, r spinal cord, 8 optic nerve, t hypo- 

 physis. In A in front of the mid-brain may 

 be seen the lower portion of the epiphysis. — 

 After T. Jeffery Parker. 



Fig. 344. A Vertical 

 section of the eye and 

 «yelids of a common 

 Lizard, B the same of a 

 Snake; both diagram- 

 matic, h cornea, o upper, 

 u lower eyelid, o bulb of the 

 .eye (in outline). — Orig. 



h-U] 



'the inner wall of the optic bulb, at the entrance of the optic nerve ; 

 in others it is absent or rudimentary. An upper and a lower 

 -eyelid are present, of which the former is only slightly movable, 

 whilst the latter can be moved across the eye as in Amphibia. The 

 .lower lid is often somewhat transparent centrally {e.g., in the common 



