Proceedings of the United States National Museum, Vol. 108

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Excerpt from Proceedings of the United States National Museum, Vol. 108: Number 3391-3410 In this paper a short description is given of a new ostracoderm, Pycnaspis splendens, new genus, new species, from the Upper Ordovician of the eastern slope of the Bighorn Mountains in north-central Wyoming. This new form is related to Astraspis desiderata from the Harding Sandstone, but it differs from the latter in the shape and microstructure of the tubercles of the exoskeleton. At the type locality it is associated with Astraspis? sp. indet. and Eriptychiida gen. and sp. indet. Exoskeletal plates referable to Pycnaspis, new genus, but at present indeterminable as to species are represented in the Winnipeg formation of the Williston Basin in Montana and in the Whitewood formation of the Black Hills in South Dakota, but such plates are missing entirely in the Harding Sandstone of Colorado. Ordovician vertebrates from North America were first recorded by Walcott who, in 1892, described small exoskeletal plates of two forms, Astraspis desiderata Walcott and Eriptychius americanus Walcott, from the Harding Sandstone outcrops near Canyon City, Colo. These two forms Walcott referred tentatively to the Asterolepidae and Holoptychiidae, respectively, but they are now generally recognized as true representatives of the Heterostraci. 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.