RIDGWAY’S catalogue of north AMERICAN BIRDS. 29 
fully up to date. It also appears desirable that an analysis 
should be given of the principal points of variance, numerical 
and otherwise, between the list which is herewith presented and 
that which has for so many years been the standard of reference ; 
while, in order to further increase the utility of the list, a brief 
review of the revisions of nomenclature which have been adopted, 
the species added to the fauna, and other matters of like interest, 
is given under appropriate headings 
“ The following enumeration contains 226 valid species and 
recognized races which have either been first described or added 
to the North American fauna since 1859, while, on the other 
hand, no less than 42 names of the old catalogue have been 
relegated to the ranks of synonymy (and 20 more removed as 
extralimital). Furthermore, of the remaining 698 names, over 
300 have been more or less emended, so that only 395 of the 
760 names as given in the old catalogue are retained in the 
current nomenclature ! 
“ In the present list only those forms which are assumed to 
be specifically distinct have separate nmnhers, the sub-species or 
races being distinguished by a letter of the alphabet ( a, et seq.) 
affixed to the species number. 
‘‘ The adoption of trinomials for the designation of nascent 
species — a direct result of the synthetic method of study which 
has supplanted the former analj^tic treatment of the subject — has 
caused perhaps the greatest difficulty encountered in the com- 
pilation of this catalogue, it being in n.any cases very difficult to 
decide whether a given form should be treated as having passed 
the ‘ varietal stage,’ and therefore to be designated by a binomial^ 
or whether it is yet incompletely differentiated, and to be 
subordinated in rank by a trinomial appellation 
“ No other method seems at all adequate to the proper 
discrimination between isolated and intergrading forms, and the 
difficulty in the cases above alluded to arises wholly from the 
