AMERICAN COLEOPTERA. 15 



Impressions within the thoracic angles well marked, hind thighs 

 very sparsely and finely punctate at middle; size smaller; 



(Rocky Mountain region) 33. obscura. 



var. prominens, var. compacta. 

 Impressions within the thoracic angles not very distinct; hind 

 thighs more coarsely and conspicuously punctate at middle; 

 size larger (Atlantic region) . 

 Prothorax more finely and evenly punctate; color black, with- 

 out trace of metallic lustre 34. tristis. 



Prothorax more coarsely and quite irregularly punctate; elytra 

 often with violaceous lustre 35. liberta. 



14. Sides of prothorax not distinctly bisinuate (except in some exam- 



ples of densicollis and fossipalpa 15. 



Sides of prothorax more or less bisinuate, the anterior sinuation 

 slight or wanting m some examples of rufa. 



Size larger (9-11 mm., , punctuation of head and thorax finer 

 and sparser; pygidium with shallow median longitudinal 

 impressed line; prosternal carina double.. .36. subcostata. 



Size smaller (8-9 mm.) ; punctuation of head and prothorax rela- 

 tively coarser and closer; pygidium not impressed; pro- 

 sternal carina single 37. rata. 



15. Front with at most a very broad and feeble post-clypeal convexity, 



usually flat or uniformly convex 17. 



Front with moderate or strong post-clypeal convexity 16. 



16. Post-clypeal convexity more or less impressed or interrupted at 



middle; elytra coarsely densely punctate; clypeal margin 

 rotundate. Atlantic region. 



Basal margin of thorax not or scarcely impressed toward the 

 hind angles 38. frontalis. 



Basal margin of thorax rather strongly impressed, especially 

 toward the sides. 

 Punctuation of thorax rather sparse, at least at middle, the 

 punctures separated by from one to two times their own 



diameters 39. excavata. 



Punctuation of thorax extremely dense and rugulose. 



40 densicollis. 

 Post-clypeal convexity not impressed at middle, the surface be- 

 hind the convexity feebly or distinctly biimpressed; elytral 

 punctuation moderate; clypeal margin feebly sinuate at 

 middle (Rocky Mountain region). 



Surface more shining, sides of prothorax more strongly rounded, 

 clypeus more advanced, elytral costas with the usual single 

 series of finer punctures 41. snbang'iilata. 



Surface less shining; sides of prothorax less strongly rounded, 

 clypeus less prominent, elytral costse almost devoid of 

 punctures 42. atratula. 



TRANS. AM. ENT. SOC, XXXV. JANUARY, 1909- 



