22 PREFACE. 
history of each species in order to designate it 
by the name applied to it by its first discoverer. 
The rule adopted is to give priority to the first 
published description or to the first published name 
accompanied by a recognizable figure, and to reject 
all claims based upon the publication of a name 
only, as these, if allowed, would inevitably lead 
to doubt and inconvenience, and in the end 
would afford opportunity for unfairness and 
fraud. The date of the first publication of the 
species is appended to the name of the work in 
which it appeared. The operation of the rule 
will restore to American authors many species 
which were first described by them, but which 
have long had a place in the works of MM. 
Ferussac, Lamarck and Deshayes under the names 
of foreigners who did not know them until after 
they had been described in this country. 
It is one of the aims of this work to point out 
the errors, and to supply the omissions, of those 
and other distinguished naturalists ; but although 
the author hopes to make his own work more 
useful thereby, he is far from presuming that it 
can bear a favorable comparison with theirs in 
any other respect than in giving a more full and 
