INTRODUCTION. 



In 1851 I was engaged, hy the Honorable Joint Library Committee 

 of Congress, to superintend the preparation of Plates for the Atlas of 

 Mammalogy and Ornithology of the United States Exploring Expedi- 

 tion; and subsequently to prepare the present volume. In both of 

 these departments of Natural History, large and highly interesting 

 collections were made, and much new and valuable information ob- 

 tained by the naturalists of the Expedition. My object has been to 

 notice, in this volume, every species of interest, with careful descrip- 

 tions of such as were previously unknown; and to give all the infor- 

 mation to be obtained from the recorded observations and journals of 

 the naturalists, which have been at my disposal; and I have appended 

 a complete Catalogue of the collections in these two classes of animals. 



Not having accompanied the Expedition, my sources of information 

 have been exclusively those designated above, and especially I am in- 

 debted to the kindness of Charles Pickering, M.D., one of the natu- 

 ralists of the Expedition, whose volumes have added so much of the 

 highest value to its series of publications. In addition to the branches 

 of Natural History with which this distinguished naturalist was espe- 

 cially charged, he made notes of observations in all other departments; 

 from which has been derived some of the most valuable material of 

 the present volume; and with great liberality and kindness, he copied 

 and collated, for my greater convenience, a large amount of manu- 

 script notes on quadrupeds and birds, made on the voyage, and now 



B 



/ 



