PREFACE. vii 



well be questioned if the only wise or proper course to emphasize 

 these slight variations is to bestow a name upon the specimen pos- 

 sessing them. Much confusion has been created by the multiplicity 

 of names that burden our nomenclature, and our difficulties are by 

 no means brushed away when one is bestowed upon some specimen, 

 any more than are these difficulties ignored if none is given; for 

 names are often not only no panacea for scientific woes, but on the 

 contrary are frequently the cause of much trouble and perplexity. 

 They are useful for the recognition of specimens possessing indepen- 

 dent distinctive characters, but if an example has none of these its 

 appellation is of little assistance. It is the extreme to which the 

 bestowal of names has been carried that is to be deprecated, not 

 the announcement of differences observed, however slight, and 

 against the former custom the Author has always protested, while 

 advocating the latter. 



It is to be expected that countries like Mexico would contain a 

 large number of animals that differ from each other in a greater or 

 less degree ; for that land probably possesses more varieties of climate 

 within a certain number of miles square than almost any other known 

 of an equal extent. The transition from a torrid to a temperate zone, 

 and again to an alpine, is accomplished in a comparatively brief 

 journey, and the several environments affect materially in certain 

 ways the animals influenced by them. So in a small extent of 

 country a number of forms allied to, but differentiated from each 

 other would be expected to occur; but whether the extreme length 

 to which the recognition of these variations has been carried by the 

 bestowal of names is either wise or necessary, may well be doubted. 



The arrangement of the Orders and Families is the same as that 

 in the "Synopsis"; but names have in some instances been changed 

 since that work was published, those heretofore employed having 

 been ascertained to be either antedated by others, or previously used 

 in this or some other branch of Zoology. Changes are continually 

 occurring in Mammalian nomenclature, and it will probably be a 

 long time before permanence in names is reached, as discoveries are 

 being made that overturn some that are constantly employed and 

 have become familiar by long use. But these changes will of neces- 

 sity become less in time and a nomenclature that at least will approach 

 stability may, in the distant future, be expected to be reached. By 

 inserting the names of the described forms in this work the Author 

 does not indorse their specific or subspecific value, and in all cases 

 where an opinion is expressed, it will be found in a footnote on the 

 page containing the form discussed. A critical review of all the 

 species and races contained in this volume and their relations to 



