File:Image from page 180 of "Water reptiles of the past and present" (1914) (14586414668).jpg

'Fig. 81.—Hydrns bicolor; sea-snake. (From Brehm)

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: condas and boas. In geological history the earliest remains known date from the latter part of the Cretaceous, and it is quite probable that they have a briefer history than that of the lizards of which they are the descendants. Venomous serpents are known only from comparatively recent geological times, and it is probable that venomosity is the latest and final specialization of importance in the reptilian class. Of strictly aquatic snakes there is no known geological history,and it is improbable that there is any such history. There are a few snakes now living—very venomous ones, allied to the deadly cobras—which have become so completely adapted to life in the water that they are unable to exist or even move about on land.These are the well-known sea-snakes of the Indian Ocean and adjacent waters. Perhaps the most highly specialized and typical of these is the black-banded sea-snake, Distina cyanocincta, which reaches a length of four or five feet, and is a rapid and excellent swimmer. From the figure (Fig. 81) it is seen that the body is very much flattened from side to side, and lacks or has but a few vestiges of the transverse scales on the under side so characteristic of all other snakes, and which enable them to move about on land.So helpless are these snakes on land that it is said sailors will handle them carelessly, because of their inability to bite while out of water,though the bite is very venomous. They never come on land for any purpose whatever, and their young, unlike those of most other snakes, are born alive. There are a number of species of these sea-snakes, though comparatively little is known of their habits.They are of especial interest as another example of the ways in which air-breathing land vertebrates have become adapted to water life. The adaptation, however, was simple, for nearly all snakes swim freely in water by undulatory movements; it wouldr

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