ORDER SAUKIA. 177 



is found, moreover, in these reptiles, the rudiment of a third 

 eyelid, but without any peculiar muscle. The third eyelid is 

 totally wanting in the cameleon, and the aperture in the veil is 

 so small, that the pupil can scarcely be seen through it. The 

 gecko has no mobile lid, and the eye is protracted only 

 by a slight fold of the skin. The same appears to be the case 

 with the skink. 



Nothing positive is known concerning the lachrymal ap- 

 paratus of the saurians. In the lizards and the cameleon, 

 the sclerotica contains osseous laminae, analogous to those in 

 birds. But these lamina do not form an anterior disk, and 

 only surround the lateral portion of the sclerotic. 



In the crocodile, the ciliary processes are very fine, and 

 well marked, each of them ending nearly in a right angle. 

 These processes are not found in the lizards. 



The iris of the saurians has some analogy with that of 

 fishes in the metallic tints with which it shines. That of the 

 crocodile exhibits a most beautiful vascular net-work. In 

 this reptile, the pupil resembles that of the cat, while it is 

 rounded in the cameleon and the lizards, and rhomboidal in 

 the gecko. 



In general, in all the animals of this order, the pupil is 

 susceptible of dilatation and contraction, so as to receive the 

 necessary quantity of light. Accordingly they can distin- 

 guish objects equally well in the obscurity of the darkest 

 and in the most brilliant light of sunshine. There is nothing 

 remarkable in the vitrea of these animals, nor yet in the 

 crystalline aqueous humours. 



In the crocodile the globe of the eye is preserved in its 

 orbit by means of six ordinary muscles arranged as in the 

 fish, and moreover, by four smaller muscles which nearly 

 embrace the optic nerve, and spread over the sclerotic. 



The organ of vision is remarkably active in the saurian 

 tribes. Inhabiting for the most part the sea-shores, and 



VOL. IX. N 



