CLASSIFICATION OF CROCODILIA. 



641 



crocodile (C. vulgaris} is still formidably common in some of the 

 fresh waters of tropical Africa. 



The eggs and the young are often eaten by a mammal called the 

 Ichneumon, and by a species of lizard. The adults have few enemies 

 except man. They seem to live in friendly partnership with little 

 birds (Pluvianus eegypticus), which remove parasites from the body, and 

 in their familiarity almost justify the account which Herodotus gives of 

 their cleaning the reptile's teeth. 



(b) The Alligators, of the genus Alligator, arc, with the exception of 

 one Chinese species, confined to N. and S. America. In N. America, 

 A. missis sippiensis, in S. America A. sclerops, is common. 



(c) The Gavials or Gharials, of the genus Gavialis, are distinguished 

 by their long narrow snout. In the Ganges and its tributaries, G. 

 gangcticus, said to attain a length of 20 ft., is common. They feed 

 chiefly on fishes. "Old males have a large cartilaginous hump on the 

 extremity of the snout, containing a small cavity for the retention 

 of the air, by which means these individuals are enabled to remain 

 under water for a longer time than females or young." 



DIFFERENCES BETWEEN CROCODILES, ALLIGATORS, 

 AND GAVIALS 



History of Or ocodilians. These giant reptiles form a decadent 

 stock. Fossil forms are found in Triassic strata (e.g. Belodon, Para- 

 suchuS) and Stagonolepis] ; their remains are abundant in Jurassic rocks. 

 In Cretaceous strata, crocodilians with proccelous vertebrae first occur, 

 the pre-Cretaceous forms having centra of the amphiccelous type. 

 The oldest crocodilians have the posterior nares situated farther for- 

 ward, behind the palatines. Huxley has worked out an "almost 

 unbroken " series from the ancient Triassic crocodilians down to those 

 of to-day. 



