INTRODUCTION 



From the foregoing it can be seen that there is a real and 

 definite need for a work of field book size which will give some 

 space, brief though it may be, to each and every recognized 

 species and subspecies of North American mammal. No 

 single volume can be expected to contain all the data required 

 by scientist and layman, and in this field book the layman is 

 considered first. Early in planning the scope of the work I 

 encountered obvious difficulties. These should be briefly 

 explained to justify the plan which has been followed. 



Scope of this Field Book 



There are 1,445 species and subspecies treated in the follow- 

 ing pages. In dealing with this large number so much space 

 has been used that the individual treatments have been con- 

 densed to the limit. The intention has been to give at least 

 one full and detailed description in each group, and then by 

 comparison or reference to this data hold the synopses of the 

 other forms of the group to the minimum of space. Often the 

 basis for separation of one species from another is of such a 

 technical nature or so subtle in character that it is most 

 difficult to describe for a lay reader. To omit completely all 

 of the forms which fall into this category would create unde- 

 sirable gaps in the field book. However, by using the geograph- 

 ical distribution as a key, one frequently is able to identify 

 these troublesome, closely related forms, because we have had 

 the distributions of the various groups worked out from large 

 series of specimens and it is fairly well known where most of 

 these animals belong. For the sake of providing a compre- 

 hensive catalogue, every North American mammal is therefore 

 listed,^ using the term North America to include all of the 

 continent north of the Rio Grande and following Miller's List 

 of North American Recent Mammals as authority. Maps to 

 show the geographical distribution of many of the species are 

 given as an aid in identification. 



Unless he be a specialist, the reader will only be confused 

 by discussions of the skull characters of mammals, and they 

 are omitted, although the greater part of the classification of 

 mammals is based upon skull characters. Frequently the 



"^ With the exception of certain of the Bears of the genus Ursus, as 

 explained on page 78. 



