. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. 444 MANUAL OF ZOOLOGY, dilia. The Gavial is distinguished by its elongated snout, at the extremity of which the nostril is placed, and by the fact that the teeth are pretty nearly equal in size and similar in. Fig 174.—Skull of young Crocodilits biporcatits (after Van der HSven). form in the two jaws. In the true Crocodiles (fig. 174) the fourth tooth in the lower jaw is larger than the others, and forms a canine tooth, which is received into a notch excavated in the side of the
. A manual of zoology for the use of students : with a general introduction on the principles of zoology . Zoology. 444 MANUAL OF ZOOLOGY, dilia. The Gavial is distinguished by its elongated snout, at the extremity of which the nostril is placed, and by the fact that the teeth are pretty nearly equal in size and similar in. Fig 174.—Skull of young Crocodilits biporcatits (after Van der HSven). form in the two jaws. In the true Crocodiles (fig. 174) the fourth tooth in the lower jaw is larger than the others, and forms a canine tooth, which is received into a notch excavated in the side of the alveolar border of the upper jaw, so that it is visible externally when the mouth is closed. In the Caimans or Alligators the same tooth in the lower jaw forms a canine, but it is received into a pit in the palatal surface of the upper jaw, where it is entirely concealed when the mouth is shut. The Crocodiles have the hind-legs bordered by a toothed fringe, and the toes completely united by membrane. They are essentially natives of fresh water, but sometimes frequent the mouths of rivers. They occur chiefly in Asia and Africa, but species are found in some of the West Indian Islands. The Alligators have the hind-legs simply rounded, and the feet not completely webbed. They are essentially aquatic, and are voracious animals, living upon fish or Mammals. The best- known species are the Alligator of the Southern United States i^A. Mississippiensis), the Caiman {A. palpebrosus) of Surinam and Guiana, and the "Jacare" or Spectacled Alligator i^A. sderops) of Brazil. The Gavial [Gavialis Gangeticus) is a native of India, and is the smallest of the living Crocodiles, attaining a length of about ten feet. True procoslian Crocodiles occur for the first time in the Greensand (Cretaceous series) of North America. In Europe, however, the earliest remains of procoelian Crocodiles are from the Lower Tertiary rocks (Eocene). It is a curious fact that in the Eocene rocks of the sou
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