8 PRELIMINARY REMARKS. 



in the regions bordering on the Pacific. No 

 extended rectifications, however, will be here 

 attempted, as it is judged best that the work 

 should represent, as it does, the state of knowl- 

 edge at the time when it was written. And we 

 leave it thus the less reluctantly, as we are 

 happy to know that the tastes and purpose of 

 the father have descended to the son, from whom 

 we may hope to receive, in due time, a critical 

 emendation and amplification of this Monograph, 

 as the fruit of his exhaustive research in the 

 same field of investigation. 



It has been thought proper, however, to insert 

 in this volume the description of one species, 

 which was accidentally omitted in its place ; and 

 also to quote the descriptions of several other 

 North American species, which have been re- 

 cently published, so as to embody all the species 

 at present known. Nearly all of them we have 

 seen, and regard them as true species. 



Editor. 



Boston, Jan. 1857. 



