vi PREFACE. 



The remarks made in the Preface of the "Synopsis," upon the 

 excessive and probably unwarranted multiplications of species and 

 races (made easy by the too liberal application of- the trinominal 

 system), may be repeated here with equal force as regards the mam- 

 malian fauna of Middle America and the various islands. 



In the examination of the many specimens rendered necessary 

 during the progress of the present work, the author has been im- 

 pressed by the fact that the "characters" of a very large number of 

 the named forms are merely comparative and not distinctive. By 

 which is meant, characters that in themselves are not sufficient to 

 identify the specimens, but render necessary the presence of exam- 

 ples of the typical form before any determination is possible, unless 

 the locality is deemed all-sufficient to fix the status. The possession 

 of topotypes of described forms for the majority of naturalists is 

 impracticable except to a very limited degree, and therefore, without 

 such aids, to accurately name specimens is, in many instances, quite 

 impossible (for even "locality" is not always to be depended upon), 

 and the effort often then degenerates into something very like guess- 

 work. Every Mammalogist must at some time have been confronted 

 with this difficulty and regretted his inability to determine his exam- 

 ples; and one naturally questions the value of a system that makes 

 such a condition possible, and doubts if the giving of names to speci- 

 mens on minute differences, which magnify slight comparative 

 characters (for often there are no others, and some of these are 

 undoubtedly due to individual variation), is scientifically war- 

 rantable or even desirable. Many specimens have been named whose 

 cranial characters consist altogether in being "longer or shorter," 

 "broader or narrower" than corresponding parts of some other 

 example, and it is easily comprehended how slight is the probability 

 that any specimen can be accurately determined whose characters 

 are such as those given (the color of the pelage also being nearly the 

 same), no topotypes of the forms with which these are compared by 

 their describer being available, and in many instances no measure- 

 ments of the crania having been given. 



It is, of course, not to be conceived that every infinitesimal 

 difference that an animal may possess can be intelligently demon- 

 strated, or that the mere bestowal of a name upon a specimen would 

 make it recognizable; and the act of naming examples that are 

 separated from their fellows on account of these minute variations 

 cannot fairly be regarded as an "accurate statement of the results of 

 organic evolution." That it is desirable that all differences observed, 

 the results of any cause whatever, should be mentioned, and in many 

 instances dwelt upon, would not be disputed by any one, but it may 



