Hayden, Ferdinand V & Leidy, Joseph; Extinct Vertebrata from the Judith River and Great Lignite Formations of Nebraska. & Geological Sketch of the Estuary and Fresh Water deposit of the Bad Lands of the Judith. American Phil. Society, vol. 11, 1859. Quarto, pp. 32, 1 map, 3 plates. In cloth and marbled boards, soiling and light wear to title page, very good.

Hayden provides his first impressions and geological observations on the "Bad Lands of the Judith". While Hayden inferrs that the geological map is colored; it is in fact black and white with 4 symbols denoting the age of the deposits. By far the most important part of this work is Leidy's description of fossils provided by Hayden. Leidy considers these to be twelve new extinct species of fishes, saurians, chelonians and mammals. Plate one contains drawings of fossil teeth of what were the first dinosaur remains accurately identified in America.