280 GEO. H. HORN, M. D. 



arcuate near the anterior angles, base nearly squarely truncate, hind angles 

 rectangular, disc moderately densely punctured. Scutellum sparsely punc- 

 tured. Elytra conjointly as wide as long, slightly narrowed posteriorly, sides 

 feebly arcuate, apices squarely truncate, surface punctured as the elytra. 

 Abdomen less coarsely and densely punctured than the elytra. Prosternum 

 very sparsely punctured, body more coarsely and densely, abdomen less densely 

 and nn)re finely than the body. Length .06 — .08 inch; 1.5 — 2 mm. 



This is our smallest species aud the only one with the margins of 

 the thorax and elytra continuous, it has therefore somewhat the out- 

 line of an Hydroporus. 



Middle and Southern States, not common. 



C COrticinuS Erichs. — Oyal, slightly oblong, pieeous, feebly shining, 

 sparsely pubescent. Head densely punctured. Thorax one-half wider than 

 long, as broad at apex as at base, sides feebly arcuate, hind angles rectangular, 

 slightly prominent, base feebly sinuate each side, surface moderately densely, 

 not coarsely punctured. Scutellum punctured at middle. Elytra a little longer 

 than wide conjointly, sides feebly arcuate, slightly narrowed to apex, disc with 

 a vague postscutellar depression, surface punctured like the thorax. Abdomen 

 above more sparsely and finely punctate. Prosternum densely and rather 

 coarsely punctured, body less densely punctured, abdomen less densely and 

 coarsely. Legs rufo-piceous. Length .12 inch; 3 mm. 



Sexual characters as in nige)-. 



This species resembles<a small niger but is known by the form of 

 the thorax and the more shining surface, and excepting its shorter 

 form resembles Ejnirxa truncatella in general appearance. 



Occurs especially in the Middle and Southern States. 



C brachypterus Say. — Oblong oval, subdepressed, pieeous, subopaque, 

 very finely and sparsely pubescent. Head moderately punctate. Thorax 

 nearly twice as wide as long, apex and base equal, sides moderately arcuate, 

 punctures of the disc rather coarse and not dense, at the sides denser and finer, 

 the interspaces alutaceous, hind angles small but distinct. Scutellum very 

 sparsely punctate. Elytra a little longer than wide conjointly, slightly nar- 

 rowed to apex, surface more finely punctured than the thorax, the intervals 

 alutaceous, punctures rather coarser near the scutellum. Abdomen above a 

 little more coarsely and sparsely punctured than the elytra. Prosternum 

 nearly smooth, metasternum coarsely but sparsely punctured, abdomen less 

 coarsely and more sparsely punctured. Length .10 inch; 2.5 mm. 



The males are known only by the additional segment. 



This species resembles mutilatus but is more elongate and has 

 quite distinct thoracic hind angles. It is also difficult to distinguish 

 from discoideus by description, but the latter is more depressed and 

 broader, aud the elytra have either a large pale elytral spot or are 

 entirely pale. 



Occurs from Pennsylvania to Canada and California. 



