CROCODILIA 201 



Living crocodiles belong to three distinct groups or families: 

 the true crocodiles and alligators; the long-snouted crocodiles or 

 Borneo ga vials; and the true ga vials of India. Members of the 

 first of these families are really only subaquatic, or amphibious in 

 habit; they move about on land with entire freedom, and often 

 seek their food there. Certain marked aquatic characters they do 

 possess, in the skull and tail, as we shall see. They are indigenous 

 to southern China, India, Africa, Madagascar, the southern part 

 of the United States, Central America, and the northern part of 

 South America. The members of this family are distinguished 

 by the more or less broad and flat head, the possession of com- 

 paratively few teeth of large size, and by having the toes less 

 completely webbed. The crocodiles proper differ from the caimans 

 and alligators especially in the arrangement of the teeth. During 

 later geological times, that is, during early Tertiary times, the 

 geographical range of the Crocodilidae was much more extended 

 than it is at present, the remains of many often very large species, 

 being found in the lake deposits of the northwestern parts of the 

 United States, Great Britain, Germany, France, etc. Yet earlier, 

 in the late Cretaceous rocks of the United States, in Texas, and 

 Wyoming especially, there have been found rather scanty remains 

 of a gigantic crocodile which must have been nearly fifty feet in 

 length when living. 



The second family, the Tomistomidae, or long-snouted croco- 

 diles, comprises but two living species, both restricted at the 

 present time to Borneo. These crocodiles have a moderately 

 slender snout, because of which they are sometimes called gavials, 

 though it is not nearly so slender as that of the true Gangetic 

 gavial. This family is probably older than either of the other 

 living ones, and is the only one known with certainty to have 

 lived during much of the Cretaceous times, several species of 

 considerable size having been found in New Jersey and Europe. 

 Their feet are better webbed than are those of the true crocodiles 

 and alligators, the front feet partly, the hind feet wholly so. 

 In general structure they seem to be the most primitive of the 

 living Crocodilia, and may have been the ancestors of all modern 

 forms. 



