I— A REVISIONAL STUDY OF THE AMERICAN 

 PLATYNIN^. 



In his synopsis of Platynus and allied genera (Proc. Acad. Phila., 

 1854, p. 35) Dr. LeConte gave a very good historical account of the 

 vicissitudes of meaning accorded the old generic names Platynus, 

 Anchomenus and Agonum of Bonelli, by various authors, alluding 

 especially to Brulle and Erichson, the former of whom placed all 

 under the name Platynus, while the latter, as well as Lacordaire, 

 preferred Anchomenus for the three united genera. The most 

 recent European list unites them all under Agonum — the third and 

 only remaining alternative. As a result of my own studies, I am 

 disposed to regard the three genera of Bonelli as sufficiently well 

 circumscribed and habitally differentiated among themselves to be 

 held as valid, and have also added some other genera, a large pro- 

 portion of the new names being rendered necessary by singularly 

 isolated neotropical types; several of these were recognized by 

 Bates as compelling the use of new generic terms, but that author 

 has, it seems, combined too many divergent forms under his con- 

 ception of the wrongly identified Colpodes, which, unless limited to 

 the more characteristic species, would admit of no accurately 

 scientific definition whatever, as a congeries of species distinct from 

 typical Anchomenus. Many of the species assigned to Colpodes 

 by Bates are purely and typically Anchomenus, where a feeble 

 inequality in the projections at the sides of the sinus in the fourth 

 tarsal joint frequently becomes evident. I have therefore limited 

 the Colpodes of Chaudoir and Bates to those species in which the 

 fourth anterior tarsal joint is very deeply and conspicuously 

 bilobed, and which at the same time possess a facies of the body 

 and character of coloration distinguishing them at least to some 

 degree from the true Anchomenus. These characters are so in- 

 definite, however, that I am forced to regard the neotropical so- 

 called Colpodes, here given the name Placodes, taxonomically as a 

 subgenus of Anchomenus, though assigning full generic value to a 

 few aberrant species placed under Colpodes by Mr. Bates. 



T. L. Casey, Mem. Col. IX, Jan. 1920. 



