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 slhght 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 
