64 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
one general work on the subject had been published, that of Audu- 
bon and Bachman on the Quadrupeds of Nortl America, which 
was issued in three volumes, from 1846 to 1854.* Immediately 
after the completion of this great work collections began to pour 
into the Smithsonian Institution from the various exploring parties 
of the Pacific Railway Surveys. This material comprised so large 
a number of new species, and cast so much light upon many pre- 
viously doubtful points concerning the relations of species already 
described, that a revision of the whole subject became necessary. 
Hence Professor Baird at once set about the preparation of the book 
commonly known as the Mammals of North America. I have already 
alluded to the manner in which it was prepared. This great work 
was rapidly pushed to completion and appeared in 1857, just three 
years after the publication of the last volume of Audubon and 
Bachman’s Quadrupeds. It constitutes the eighth volume of the 
Pacific Railroad Reports, and is a ponderous quarto of more than 
800 pages, accompanied by numerous excellent plates. 
Though published thirty years ago, this work still remains the 
standard general treatise on North American mammals. It con- 
tains no biographical matter, but consists wholly of technical de- 
scriptions. It treats of all the mammals then known from the 
. continent of North America north of Mexico, except the bats and 
the truly pelagic forms—whales, sea cows, and seals. The total 
number of known species was increased nearly twenty-five per 
cent. 
In fullness of synonymy, and in the correct assignment of species 
previously described, Professor Baird was much in advance of pre- 
vious workers. The descriptions, which are models of painstaking 
accuracy and precision, are taken from the specimens themselves, 
and are accompanied by long tables of measurements, the value of 
which more than justifies the enormous expenditure of time neces- 
sary in their preparation. Much more attention was paid to crani- 
ological characters than had been the custom with previous writers, 
which fact contributes largely to the permanent value of the work. 
Professor Baird’s long training as a careful observer, his power 
of concentrating his knowledge of matters under investigation, the 
*The volume on Mammals of Richardson’s Fauna Boreali Americana 
does not fall under this head, because it treats only of the northern portion 
of the continent. 
