ceedings" of the Academy. The extent to which Dr. Leidy was absorbed in his paleontological studies, between the years 1854 and 1872, may be judged by the fact that, out of seventy-two communications published during that period, only thirteen were on the subjects to which he had formerly devoted his attention, and these were, for the most part, brief reports of verbal communications made before the meetings of the Academy.
In 1869 his memoir entitled "The Extinct Mammalian Fauna of Dakota and Nebraska" appeared as the seventh volume of the journal of the Academy. The work, a quarto of 472 pages, illustrated by thirty lithographic plates, is the result of the gradual accumulation of material during twenty-three years. This elaborate work was followed in 1873 by one of equal importance, under the title "Contributions to the Extinct Vertebrate Fauna of the Western Territories." It forms the first volume of the superb quarto reports of the survey of the Territories, under Dr. Hayden, and consists of 354 pages and thirty-seven plates.
For many years after the publication of his paper on fossil horses, in 1847, Dr. Leidy was almost the only American author whose attention was given to the study of the extinct vertebrata. The wonderful remains brought to light by the explorations under the direction of Dr. Hayden had, however, excited the interest of others, and private expeditions, as well as the official surveys, had collected rich stores of vertebrate fossils, in some cases from the same localities whence came the material submitted to Dr. Leidy's examination. The anxiety to obtain early publication of descriptions of supposed new forms became so great that, in at least one instance, such description was telegraphed to a learned society from the field. The dispatch was published with as little delay as possible, but the paragraph contained so many errors that the experiment has not, we believe, been repeated. In the attempt to settle questions of priority, the published arguments became so bitter and the personalities indulged in so pronounced that Dr. Leidy, who had been able to refrain from taking part in the controversy, finally withdrew from the field. With characteristic amiability, he had remarked in the preface to his last-named work: "The investigations and descriptions of some fossils from the same localities have been so nearly contemporary with my own that, for want of the opportunity of comparison of specimens, we have no doubt in some cases described the same things under different names, and thus produced some confusion which can only be corrected in future." And, while others were making anxious inquiries regarding dates of issue, and personal bulletins were followed rapidly by bitter little notes of reclamation, he placidly held to the belief that the future would undoubtedly award the credit where it belonged, and withdrew to resume the studies which he had prosecuted so successfully in former years. The only paleontological communication of importance which
