File:Image from page 231 of "Water reptiles of the past and present" (1914) (14772758182).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: vex, some opisthocoe-lous, and some procoelous.And Dr. Hay tells us thatthe neck has increased inlength in the later forms.The skull also is verypeculiar in that it hassome very primitive char-acters and others veryaberrant. The temporalroof, as has been said, hasno holes through it, thoughit is often reduced by theemargination of theborders, whether from be-low or behind, until insome the whole temporalregion is exposed, and notat all covered over. Thereis no parietal foramen, soconstantly present in all the early reptiles and in the lizards andthe tuatera of modern times. There are no teeth or vestiges ofteeth, but the jaws have usually a horny cutting edge, which seemsto be quite as serviceable; in the river turtle the lips are fleshy.There is no transverse or transpalatine bone. There is a singlevomer only, not paired as in other reptiles, whence comes thedoubtful theory that the vomers of other reptiles are not the realvomers originally so named in mammals, and hence often called

Text Appearing After Image: Fig. [114.—Pelvis of Chelone, from below:pu, pubis: is, ischium; il, ilium (in acetabulum). CHELONIA 221 prevomers. The vomer of the turtles under this theory is believedto be the real homologue of the mammalian bone. The palate isalways slightly, sometimes nearly wholly, underfloored, as in mam-mals, carrying the internal nostrils far back in the mouth. In theoccipital region of the skull there is a separate bone on each sidecalled the paroccipital or opisthotic, which has been indistinguish-ably fused with the exoccipital in all other reptiles except the ich-thyosaurs since Triassic times. ..prnx

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