c 
Ven 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 rests 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 systematicaily 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- 
