iv* MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



entire collections of Rodents contained in these Museums, amounting in the 

 aggregate to several thousand specimens. No work of the kind hitherto pub- 

 lished n\s(s upon such an enormous amount of material, and no naturalists are 

 more competent to elaborate it than the authors of these memoirs have proven 

 themselves to be. Their work, it is believed, will challenge comparison in 

 points of laborious and conscientious research, of accurate and minute detail, 

 and of thoroughly scientific method in study. 



The Rodentia constitute by far the largest order of Mammals, and one 

 of the most important from an economic as well as scientific standpoint. 

 Though the species are mostly small and apparently insignificant, their rela- 

 tions with man are of much moment. Some of them, like the Beaver, the 

 Muskrat, and others, furnish important articles of commerce ; while a large 

 majority of the species directly affect the agricultural interests of the nation. 

 Various species occur in countless multitudes, and constitute one of the most 

 serious obstacles with which the agriculturist has to contend in many parts 

 of the country. It is not easy, therefore, to give undue prominence to a 

 group of Mammals, accurate and full information respecting which is essen- 

 tial to the intelligent direction of measures to stay their ravages. In the 

 present work, the technical history of all the species known to inhabit North 

 America is presented in full, together with their geographical distribution 

 and, in some cases, their habits. The fossil as well as the recent species are 

 considered, and many of the exotic allies, of Mexico and of Central and 

 South America, are also brought under review. 



It is now twenty years since the Rodents of North America were revised 

 by Professor Baird, in his "Mammals of North America". This interval 

 almost exactly coincides with the period of the rise and establishment of the 

 theory of evolution, or latest scientific views of the development of species, 

 and their variability under climatic and other conditions of environment. The 

 Rodents of North America have never before been systematically treated from 

 this standpoint, which necessitates a thorough revision of the whole subject. 

 The authors have thus not only been able to avail themselves of a vastly greater 

 amount of material than that at the command of any other investigators, 

 but they have also studiously applied the sounder principles of modern sci- 

 ence to the elucidation of the subject. They are well known as leaders 

 among American Mammalogists in this line of research, and their studies 

 have resulted in placing the subject in an entirely new light. It is believed 

 that the publication of this volume will mark an era in the history of Ameri- 



