File:Image from page 245 of "Water reptiles of the past and present" (1914) (14772774472).jpg

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: pendently in modern turtles, unite with each other at an earlyday. But it was incredible that the largest of known turtles shouldbe but just hatched, and for this and other reasons it has been con-cluded that this ancient mariner is one of those forms, not un-common in old days, whose incompleteness in some respects pointsto the truth of the belief that animals have assumed their modernperfection by a process of growth from more simple beginnings. 234 WATER REPTILES OF THE PAST AND PRESENT Later studies by Doctors G. Baur, E. C. Case, 0. P. Hay, andespecially G. R. Wieland, of the abundant and excellent material,preserved in the museums of Yale and Kansas universities andthe Carnegie Institution, and especially the discovery by Wielandin 1895 of an allied and yet larger form which he called Archelon,have determined practically every detail of the structure of thisremarkable group of sea-turtles. A surprisingly complete speci-men of Archelon is mounted in the museum of Yale University.

Text Appearing After Image: Fig. 123.—Archelon ischyros; skeleton from above: n, nuchal, r, r, r, ribs; m,m,peripheral bones; h, humerus; r, radius; u, ulna; t, tibia; fi, fibula. (From Wieland.) About a half-dozen species and two genera of the family haveso far been described, all coming from the Upper Cretaceousdeposit of Kansas and South Dakota, the genus Archelon from laterrocks than those which have yielded Protostega. The general form and structure of Archelon will best be under-stood from the accompanying figures after Wieland (Figs. 123,124, 125) and the restoration of the living animal as interpretedby the writer (Fig. 126). If the leather-back turtle, described CHELONIA 235 farther on, is really the descendant of these or allied turtles, as many-authors believe, it of course represents the very highest aquaticspecialization of all Chelonians. If, on the other hand, as somebelieve, the leather-back is the end of a long and independent lineof descent, then Archelon represents the highest aquatic specia

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