Report Upon United States Geographical Surveys West of the Hundredth Meridian Vol. IV- Paleontology (Parts I & II) ; Engineer Department, U S Army. Part I: Report Upon the Invertebrate Fossils Collected in Portions of Nevada, Utah, Colorado, New Mexico, and Arizona, by Parties of the Expeditions of 1871, 1872, 1873, and 1874. Part II: Report Upon the Extinct Vertebrata Obtained in New Mexico by Parties of the Expedition of 1874

Paleontological results from the collections and examinations of made during the years 1871, 1872, 1873, 1874, And 1875, in connection with geographical explorations and surveys west of the 100th meridian, for publication as Volume VI of the reports authorized by acts of congress approved June 23, 1874 And Feb 15, 1875.
Part I is by Dr. C.A. White, on the collection if invertebrate fossils, numbering 183 distinct species, of which 50 are new to science. A preliminary report, with descriptions of new species is embodied in the present volume.
Part II is comprised of a similar treatment of the vertebrate fossil collections, by Prof E.D. Cope,
The plates illustrating the invertebrate fossils were drawn by Mrs H. M. Martin.
Summary of the Table of Contents: Part I: Classification - Fossils of the following perioods: Primordial, Canadian, Trenton, Subcarboniferous, Carboniferous, Jurassic, Cretaceous, Tertiary. Part II: Geology of Mesozoic and Terriary beds and fossils of the Mesozoic periods, beds, Eocene plateau, Loup Fork beds, Mesozoic Vertebrata / Fossils of the Eocene period, Pisces, Reptilia, Aves, Mammalia; Bunotheria, Rodentia, Amblypoda, Perissodactyla; Fossils of the Loup Fork epoch: Reptilia, Aves, Mammalia, Rodentia, Carnivora, Proboscidia, Perissodactyla, Artiodactyla.