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Identifier: waterreptilesofp1914will Title: Water reptiles of the past and present Year: 1914 (1910s) Authors: Williston, Samuel Wendell, 1851-1918 Subjects: Aquatic reptiles Publisher: Chicago, Ill., The University of Chicago Press Contributing Library: Boston Public Library Digitizing Sponsor: Boston Public Library

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Text Appearing Before Image: pebbles, as domany birds. There is an oldmyth that the crocodile of theNile swallows a pebble on eachof its birthdays, thus giving reliable information as to its age bythe number found in its gizzard at its death! And this habit hasbeen suggested for some of the most ancient crocodiles, the teleo-saurs, by the recurring presence of siliceous pebbles found withthe remains of their skeletons. And we have seen this pebble-swallowing habit was also characteristic of the plesiosaurs, withwhose remains stomach-stones, or gastroliths, as they have beencalled, are often found. All of these various characters of the skeleton and fleshy partsare pretty conclusive evidence that the crocodiles, ugly creaturesthat they are, today enjoy the highest rank among cold-bloodedanimals. They are perhaps in some respects of not so high a typeof reptiles as were some of the extinct reptiles, but that they havesurvived so long, so many millions of years, is pretty good evidenceof endurance, to say the least.

Text Appearing After Image: Fig. 104.—Pelvis of crocodile: il, ilium;is, ischium; pu, pubis. CROCODILIA 201 Living crocodiles belong to three distinct groups or families:the true crocodiles and alligators; the long-snouted crocodiles orBorneo gavials; and the true gavials of India. Members of thefirst of these families are really only subaquatic, or amphibious inhabit; they move about on land with entire freedom, and oftenseek their food there. Certain marked aquatic characters they dopossess, in the skull and tail, as we shall see. They are indigenousto southern China, India, Africa, Madagascar, the southern partof the United States, Central America, and the northern part ofSouth America. The members of this family are distinguishedby the more or less broad and flat head, the possession of com-paratively few teeth of large size, and by having the toes lesscompletely webbed. The crocodiles proper differ from the caimansand alligators especially in the arrangement of the teeth. Duringlater geological times, tha

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