The Fauna Of The Keyser Member Of The Helderberg Formation In Maryland

Author : Thomas Poole Maynard
Publisher : Forgotten Books
ISBN 13 : 9781330383674
Total Pages : 59 pages
Book Rating : 4.3/5 (836 download)

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Download or read book The Fauna of the Keyser Member of the Berg Formation in Maryland written by Thomas Poole Maynard and published by Forgotten Books. This book was released on 2015-06-25 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from The Fauna of the Keyser Member of the Berg Formation in Maryland: A Dissertation Submitted to the Board of University Studies of the Johns Hopkins University, in Conformity With the Requirements for the Degree of Doctor of Philosophy They increase toward the margin by implantation. The striæ may be alternately coarse and fine, or there may be several fine striæ between the coarser ones. Internally the ventral valve is not usually well preserved. The vascular area is small and not usually well defined. The teeth which diverge from the beak, are prominent, rounded, and become thicker towards their extremities. In the dorsal valve the cardinal process is prominent and on both sides of it are strong divergent dental lamellæ which are produced forward and extend to at least the middle of the valve, converging toward the central prominent ridge which extends from beneath the beak to the base, and circumscribes a suboval muscular area. Dimensions of an average specimen: Length 6.5 mm.: width 8 mm. Dalmanella clarki may be distinguished from Dalmanella postelegantula of the Decker Ferry in being smaller while the sinus of the brachial valve extends from the beak to the front. It differs from Dalmanella elegantula of the Clinton and Niagara in being wider than long, while the brachial valve is more convex and the mesial sinus more conspicuous. It differs from Dalmanella subcarinata in having the brachial valve more convex, but not subcarinate. Occurrence. - Helderberg Formation, Keyser Member. Cash Valley. Collection. - Maryland Geological Survey. Description. - "Shell longitudinally semielliptical: valves unequally convex: hinge-line straight, with the extremities subangular. Dorsal valve convex, with a depression from beak to base, on each side of which the shell is more convex, and thence sloping somewhat abruptly to the sides: beak very small and scarcely incurved. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.