Coleopterological Notices, V. 393 



Prothorax rectangular, one-half wider than long, the sides parallel, 

 very feebly arcuate ; median groove feeble, the others almost com- 

 pletely obsolete. Elytra distinctly wider and longer than the pro- 

 thorax, flat. Length 2.5 ram. ; width 0.75 mm. District of 

 Columbia. 



Of this distinct and myrmecophilous species I have only seen 

 the female. The mentum is smooth and polished, with a trans- 

 verse, feebly arcuate broad and irregularly eroded subbasal groove, 

 and the usual membranous apical margin. 



O. densus n. sp. — Parallel, rather narrow, strongly shining, glabrous, 

 tlie tergum with very minute sparse hairs, the venter minutely and extremely 

 remotely pubescent ; pronotum rufous ; elytra darker, piceous ; head and 

 abdomen black ; legs pale flavate ; antennae blackish, pale toward base ; 

 punctures throughout the head, pronotum and elytra rather coarse, very 

 dense, subcoalescent ; separated longitudinally by anastomosing rugae, the 

 front between the antennal prominences shining and subimpunctate ; abdo- 

 men polished throughout, very minutely remotely and obsoletely punctulate. 

 Head very slightly narrower than the prothorax, a little wider than long, the 

 occiput feebly, remotely biimpressed at base only; eyes small, convex, at 

 one-half more than their own length from the basal angles ; tempora nearly 

 straight and parallel behind them to the rounded basal angles, thence sub- 

 transverse to the neck ; antennae nearly as long as the head and prothorax, 

 the basal joint cylindrical, as long as the next three, second much stouter 

 than the third, outer joints moderately incrassate, tenth one-half wider than 

 long, eleventh as wide and long as the two preceding, ogival. Prothorax nearly 

 twice as wide as long, widest near apical third, the sides parallel, broadly, 

 evenly arcuate from the apex to the antebasal notch, the latter distinct; base 

 narrower than the apex, arcuate, the latter truncate ; disk tmusually convex 

 toward the middle, the median groove deep, the others obsolete, not impressed 

 toward the sides. Ehjtra slightly wider and much longer than the prothorax ; 

 sides divergent, broadly arcuate behind ; humeri exposed ; disk flat. Abdomen 

 a little narrower than the elytra ; sides parallel ; border moderately deep, 

 rather thin toward base, gradually very thin behind the middle. Length 

 1.9-2.1 mm. ; width 0.5 mm. 



Maryland ; Texas. 



Possibly also myrmecophilous, somewhat resembling placusinns 

 but much smaller, with the abdomen polished, much less pubescent 

 beneath, and the prothorax short, narrowed and laterally emargi- 

 nate near the base. The female has the head smaller and shorter 

 and the eyes relatively larger, situated at not more than their own 

 length from the base. In the male the seventh ventral plate is 

 broadly bisinuate at apex, the median lobe feeble but obtusely an- 

 Annals N. Y. Acad. Sci., VII, Nov. 1893.— 26 



