File:Image from page 19 of "Water reptiles of the past and present" (1914) (14586324708).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: reviously imperfectly known. It is commonly, but erroneously, believed that the bones ofextinct animals are usually found in excavations made for the pur-pose. It is true that not a few specimens of fossils have beendiscovered in excavations made for other purposes, such asrailway cuttings, quarries, wells, etc., but if no others were foundour knowledge of the animals of the past would be very meagerindeed. Fossils are, for the most part, found by deliberate search s WATER REPTILES OF THE PAST AND PRESENT over the denuded rocks in which they occur. Methods of searchand collection will best be understood by the following descriptionof the noted fossil-bearing rocks of western Kansas. About the middle of Cretaceous times, there extended from theGulf of Mexico on the south to or nearly to the Arctic Ocean onthe north a narrow inland ocean or sea, a few hundred miles inwidth, covering what is now the western part of Kansas and theeastern part of Colorado, and separating the North American

Text Appearing After Image: Fig. i.—A characteristic chalk exposure in western Kansas, a hundred acres ormore in extent. continent into two distinct bodies of land. This ocean, because ofits location, bordered on both sides by low-lying lands—the RockyMountains had not then been pushed up—doubtless was compara-tively calm and placid, free from violent storms and high tides.That the climate, in the region of Kansas at least, was warm oreven subtropical is fairly certain, since plants allied to those nowliving in warm, temperate, or subtropical regions were then livingmuch farther to the north; and since the animals which then INTRODUCTION g lived in this sea were only such as would be expected in waters ofwarm temperature. Its tributary rivers could have been neitherlarge nor swift-flowing, since the sediment at its bottom was free,or nearly free, from in-brought material. This was at least thecase not very far from its shores. Its slowly falling sediment wascomposed, almost exclusively, of microscopic shelwaterreptilesofp1914will

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