446 



CROCODILIA 



carries a flap of skin, provided with muscles, to close the ear 

 tightly. The tympanic membrane is visible at the bottom of 

 the recess; shining through it is part of that cartilage which is 

 homologous with the malleus of the auditory ossicular chain ; 

 the outward extension of the latter on its way to the mandible, 

 behind the joint, passes as a partly cartilaginous string through 

 the slit-like hole which is visible at the back of the skull, 

 between the quadrate and the latero-occipital wing. 



The eyes have, besides the lower and upper lid, a third, the 

 nictitating membrane, which can be drawn over the front of the 

 eyeball. In the upper lid lies a cup -shaped bony plate of 

 variable size. The pupil contracts into a vertical slit. The iris 

 is greenish. 



^=. CROCODILES. IHHIIil ALLIGATORS. 



FIG. 104. Map to illustrate the present distribution of Crocodilia. 



The recent geographical distribution of the various kinds of 

 Crocodilia loses its mystery when we recollect that during the 

 Tertiary period Alligators, Crocodiles, and long-snouted Gavials 

 existed in Europe. The solitary species of Alligator in China is 

 the last living reminder of their former Periarctic distribution. 

 The group, taken as a whole, is otherwise now intertropical, 

 Crocodiles alone inhabiting the Palaeo-tropical region, together 

 with long -snouted forms in the Oriental sub -region, while 

 Alligators and Caimans, with a few Crocodiles, live in America. 



They are all rapacious, doing much damage by their pre- 

 datory habits, and are fierce and sulky in temper. But the 

 danger to man differs much in different countries. While Croco- 

 diles are dreaded in some localities, they are in others considered 

 almost harmless, and men swim through the haunted waters 

 without hesitation. It seems as if certain old and wily indivi- 

 duals turn into man-eaters, just like tigers and lions. 



