June i 9 oo.] Casey: On North American Coleoptera. 109 



and purely characteristic structural characters, and is therefore valid. 

 It differs from Atomaria in the characters stated in the table, and the 

 habital differences are such that it is seldom a matter of doubt as to 

 the proper genus at the first glance. The body is elongate, generally 

 quite slender and subparallel, convex and subuniformly, sparsely 

 clothed with short and subdecumbent hairs, which become gradually 

 still shorter in a sutural region near the elytral apex. The antennae 

 and eyes are moderately developed, the former generally rather stout, 

 with more pronounced club than in Atomaria, and the joints of the 

 shaft also very conspicuously alternating in length ; the eyes are never 

 very prominent and are not very coarsely faceted. The species are 

 numerous in North America, relatively more so, apparently, than in 

 Europe, where they are greatly outnumbered by Atomaria. Although 

 easily separable by sight as a rule, they are even more homogeneous 

 in adherence to a fixed type form than in Atomaria, and consequently 

 form a difficult study for the taxonomist, as the differences are nearly 

 all comparative. They seem to be quite local in distribution, judging 

 from the material at hand excepting crassula which is common to the 

 Atlantic and Rocky Mountain regions, and therefore fall very satis- 

 factorily into primary geographic subdivisions as follows : — 



Species of the Appalachian regions and Great Lakes : 2 



Species of the Rocky Mountain system 6 



Species of the Pacific Coast regions 15 



2 — Pronotum impressed at basal only in median half, the basal bead bordered by 

 coarse punctures, especially pronounced within the impression, the latter with 

 clearly defined lateral limits ; body small, elongate-oval, convex, polished, pice- 

 ous, the elytra somewhat paler, the legs and antennae flavo-testaceous ; pubes- 

 cence short and very sparse ; prothorax slightly transverse, the sides broadly 

 arcuate and feebly converging from basal fourth, narrowed at base, the punctures 

 notably sparse and rather coarse ; elytra about three-fifths longer than wide, 

 somewhat prominently rounded and subinflated at the middle, then rapidly nar- 

 rowed, the punctures sparse, strong and moderately coarse. Length 1. 25-1. 35 



mm.; width 0.5-0.55 mm. Michigan Sllbnitens, sp. nov. 



Pronotum more or less distinctly impressed along the basal margin throughout the 



width 3 



3 — Elytra variegated in color, red, a small post-scutellar transverse spot on the suture, 

 a large entire fascia behind the middle, fainter toward the suture, and the apex, 

 black, remainder deep black, the legs and antennae testaceous ; body small, elon- 

 gate-oval, strongly convex, highly polished ; antennas well developed, half as long 

 as the body ; prothorax feebly transverse, nearly as in subnitens, finely but deeply, 

 very sparsely punctate, the basal impression stronger toward the middle ; elytra 

 feebly though subprominently inflated at the middle, then rapidly narrowed to 



