146 The Alligator and Its Allies 



Us. " This reservoir is of irregular form and opens 

 forwards into the base of the nasal cavity proper. 



The third type of gland mentioned above, the 

 conjunctival, is found on the lower eyelid where 

 the conjunctiva passes from the lid to the eyeball. 

 The gland is of a "scattered acinose" type. 



The usual muscles of the eyeball are found in 

 the Crocodilia. The four rectus and two oblique 

 muscles have about the usual arrangement and are 

 attached to the eyeball by very short aponeuroses. 

 The retractor oculi muscle is only weakly developed. 

 It consists of two separate bundles which, lying 

 behind the optic nerve, arise from the forward bony 

 wall of the socket and are inserted on the sclera 

 very near the optic nerve. 



The eyeball consists of the usual layers, includ- 

 ing, as might be expected from the nocturnal habits 

 of the Crocodilia, a typical tapetum lucidum. 



In the sclera, instead of the bony ring common 

 to the saurians, is found a well-developed cartilage 

 covered with the fibrous layer of the sclera ; the 

 fibers of this layer are arranged into two more or 

 less distinct layers. 



While not worked out in detail the cornea consists 

 of the usual five layers. 



';In the iris the musculature is less developed than 

 in the birds; Bronn thinks this may be compen- 

 sated for by the greater development of the 

 ' vascular structures. " 



The pupil is a vertical slit. 



