File:Image from page 64 of "Water reptiles of the past and present" (1914) (14586350808).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: e bone-bed in black shale inthe immediate valley of the Kaskaskia River near Danville. Theknown fossils from this bone-bed—all isolated bones—are preservedin the museum of the University of Chicago, and include the typesof several genera later recognized in the Texas deposits. THE AGE OF REPTILES 53 The deposits of Texas, extending northward through Oklahomato the south line of Kansas, are of considerable extent, for the mostpart lying along the Wichita River and its tributaries, north ofSeymour, Texas. They are composed chiefly of red clays andsandstones of fresh-water or delta origin, perhaps eight hundredfeet in total thickness. Beds of like character and yielding similarfossils are also known from northern New Mexico on the tributariesof the Chama River. Their chief characters, as well as restorationsof some of the more noteworthy forms, have already been given. No vertebrate fossils are known in America from the UpperPermian and Lower Triassic. Marine limestones of Middle and

Text Appearing After Image: Fig. 20.—Restoration of Varanops, a theromorph reptile from the Permian ofTexas; about four feet long. Upper Triassic age of Nevada and northern California have yieldednumerous remains of primitive ichthyosaurs, the only known re-mains of the thalattosaurs, and a few others of doubtful affinities,all of which have been described by Dr. Merriam. The UpperTriassic exposures, of considerable extent, occur between the PittRiver and Squaw Creek in Shasta County, California. Reptilianremains from the Middle Triassic are so far known only from thelimestones of West Humboldt and New Pass regions of western andcentral Nevada. Land reptiles of Middle and Upper Triassic age are known frommany widely separated localities in the United States, but chieflyfrom the extensive red beds of the Rocky Mountain region. 54 WATER REPTILES OF THE PAST AND PRESENT The fossils from these beds occur for the most part at least in thehorizon called the Shinarump. Its age is usually considered to beUpper Triassi

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