CROCODILES, ALLIGATORS, ETC. 43 



those of the latter being invariably webbed, those of the 

 former usually so. Only the three inner digits are clawed. 

 The compressed tail is a powerful organ, mainly adapted 

 for propulsion in the water, but serving also as a 

 powerful weapon of attack and defence. 



From lizards, with which they were formerly associated. 

 Crocodiles differ in various important anatomical characters, 

 the ribs, for instance, being forked at the articulation with 

 the vertebrae, while the abdomen is as, in Sphenodon, 

 protected by transverse series of bones. 



Crocodiles and Alligators are mainly carnivorous, feeding 

 on mammals and waterfowl, for which they lie in wait 

 close to the edge of the water, sweeping them in by a blow 

 of their tail. The Gharials throughout life feed almost 

 exclusively on fish. All are oviparous, laying oval, hard- 

 shelled eggs, which are often deposited in " nests," con- 

 structed and watched over by the female, and, in the 

 majority of cases, incubated by the heat of the sun. The 

 embryo Crocodile is provided with a large " egg-tooth," 

 situated at the extreme end of the snout, its function being 

 to help in cutting through the hard shell. This " tooth " 

 soon becomes loose, and is shed a day or two after birth. 

 The young are most aggressive immediately they leave the 

 tgg, snapping and biting after the manner of their parents. 

 Most species hibernate or estivate in the mud on the 

 banks of the rivers or ponds for at least three months in 

 the year. 



The order is represented throughout the tropical and 

 semi-tropical parts of the globe by the single family, the 

 Crocodilid^, which embraces six genera, viz. Alligator^ 

 Caiman, Crocodilus, Osteolcemus, Gavialis, and Tomistoma. 



