PREFACE. 



The present report is intended to embrace a systematic account of all the species of North 

 American mammals collected or observed by the different parties organized under the direction of 

 the War Department for ascertaining the best route for a railroad from the Mississippi river to 

 the Pacific ocean. It was originally proposed to furnish a separate report in detail, on the 

 collections of each party, but a consideration of the fact that, with scarcely an exception, almost 

 every species was found on two or more lines of survey, and thus not peculiar to any one expe 

 dition, led to an abandonment of the first intention. It was considered to be worse than useless 

 to repeat the same descriptions and details over and over again, while, at the same time, under 

 the circumstances, it would have been difficult to say in what report any particular article could be 

 best placed. As, too, the interest of North American zoology depends not merely on the character 

 of the species, but also on their generic and family affinities, as well as on their relationships to lati 

 tude and longitude, climate, soil, elevation, &c., it would have been impossible to do justice to the 

 subject by cutting up the report into several isolated portions without any special connexion as 

 parts of a systematic whole. 



At the same time, however, as it was desirable to present a picture of the zoological character 

 of the several routes, as well as to show what each party accomplished, and as many very im 

 portant notes of habits and local peculiarities were made by the naturalists of the different lines, 

 it would have been clearly an act of injustice to these gentlemen as well as to their chief officers 

 to merge all their results into one common report. For these and other reasons it was finally 

 determined that there should be prepared one general report on the entire collections of the 

 railroad surveys, to consist solely of the technical description of the families, genera and species, 

 and of such remarks as might be necessary to show their place in the systems, each species to be 

 preceded by its synonymy, and followed by an enumeration of all the specimens collected, so 

 arranged in tables as to show their geographical distribution. 



In addition to this general report, however, special reports by the naturalists of each line were 

 also to be prepared and published, to embrace the systematic and vernacular names of their 

 species, with a list of the specimens collected. To these special reports were to be confined all 

 the biographies of the animals seen, all notices of their habits, peculiarities, and distribution, as 

 observed and recorded during the route. In order, that there might be no misconcep 

 tion of the species referred to, it was concluded to give a short diagnosis of each with a 

 reference to the page of the general report where the purely zoological details might he found 

 more at length. 



The present report, therefore, is the first of the series of general reports referred to, to be fol 

 lowed as soon as practicable by the remainder of the Vertebrata. The special reports on the 

 zoology of each line of survey will be found in connexion with the other reports belonging to 

 their respective parties, and, in their full notices of the life of our western animals, possess 

 L 4* 



