PREFACE 
TO THE FIFTH EDITION. 
Tuts book is designed to give to students and collectors 
aready means of identifying the Vertebrate fauna of the 
region which it covers, and of recognizing the characters 
on which the families, genera, and species of these ani- 
mals are founded. 
To these ends, I have made use of a system of analyti- 
cal keys by which differential characters are brought into 
contrast. The usefulness of such keys has long been 
recognized by botanists, and in ornithology the recent 
works of Coues and Ridgway have proved their value to 
the student. 
That the book might not reach a size too large for field 
or class use, I have made all descriptions very concise, 
with as few repetitions as possible. I have confined the 
generic characters to the analytical keys, using as a rule 
only such characters as are distinctive as well as descrip- 
tive. The need of condensation has caused the omission 
of synonymy, and of references to authorities except in 
special cases. 
In the first four editions of this work (1876, 1878, 1880, 
1884), large use was made of artificial characters in the 
analyses of the genera. The use of such characters is 
often a help to quick identification of species, but with 
the disadvantage of hiding from the student the real char- 
acters on which classification is based. In the present 
edition, these artificial keys have been chiefly set aside, 
