PLATVMN.i: 99 



There are, however, exceptions as might be expected, the prothorax 

 in atromicans, for instance, being noticeably subcordiform, though 

 with broadly rounded or subobsolete basal angles, but in all such 

 cases the relative widths of the prothorax and elytra are the deter- 

 mining factor, and it is but seldom that a species cannot be assigned 

 satisfactorily to either Anchomenus or Agonum. So in my opinion 

 all the genera of Bonelli are worthy of continuance, at least from 

 the important standpoint of general habitus, and, for taxonomic 

 reasons, it is better so, because to unite all these elements would 

 give us a supergeneric aggregate, so large and heterogeneous as to 

 hamper rather than aid the process of naming what may ultimately 

 prove to be thousands of specific forms. In our fauna four groups 

 are definable as follows: 



Outline elongate-oval; surface convex, pallid, with darker median parts 

 of the disk; elytra with more or less evident scattered interstitial 

 punctures, the dorsal punctures five to eight. Pacific coast regions. 



I (maculicolle) 



Outline more parallel; surface generally less convex 2 



2 — Upper surface more or less brilliantly metallic in lustre; dorsal 

 punctures three to about six in number II {cupripenne) 



Upper surface black and without marked metallic lustre, this however 

 feebly aeneous in a few, such as metallescens and renoicum, the 

 anterior parts often feebly greenish in placidum and allied forms 

 and entirely green in errans 3 



3 — Integuments thick; pronotal fovese as in the cupripenne group, at 

 some distance from the sides and not formed partially by the 

 reflexed margin Ill (melatiarium) 



Integuments thin; pronotal foveae large, concave, formed externally by 

 the more widely reflexed side margin IX'^ (placidum) 



The second and third groups extend entirely across the continent 

 from the Atlantic to the Pacific, and the fourth from the Atlantic 

 to the Rocky Mountains and far into the Sonoran regions of the 

 southwest and Mexico. The cupripenne and melanariiim groups 

 form the larger part of the genus, the others being composed of but 

 few species so far as known. 



Group I — maculicolle 



Subgenus Leucagoniun nov. 



In the fauna of the southern Pacific coast regions there are 



several distinct species of this group, all formerly confused with 



maculicolle. The comparatively minute variolatum, of LeConte, 



