1873.] IdO [Horn. 



H, tesselatus, Zieg. Proc. Acad. 1844, p. 44 ; Lee. (Sperchopsis) Class. 

 Col. N. A. p. 47. 



Pale castaneous, shining, elytra with small piceous spots irregularly 

 disposed. Head coarsely and sparsely punctured. Maxillary palpi with 

 the last joint longer than the third and nearly as long as the second. 

 Thorax two and a half times as wide as long at middle, sides moderately 

 arcuate, at anterior angles strongly arcuate, apex deeply emarginate, base 

 broadly rounded ; surface feebly convex, coarsely and sparsely punctured. 

 Elytra broadly oval, nearly as broad as long, very convex transversely and 

 longitudinally, margin explanate : surface striate, striae coarsely punc- 

 tured, intervals convex, the alternate intervals beginning with the first 

 more convex at apex. Body beneath black, legs piceous, femora at 

 apical half glabrous. Length .28 inch ; 7 mm. 



There are no characters by means of which this species can be separated 

 from Hydrobius ; the palpi are precisely those of well known species of 

 that genus. The facies of the species is however totally unlike any thing 

 else in the genus. The longitudinal aspect is very convex, the thorax 

 strongly deflexed, the elytra more elevated behind the scutellum and then 

 suddenly descending. Viewed laterally the elytral and thoracic margins are 

 not continuous but form an angle with each other. The mesosternum is 

 simple, the presternum slightly carinate, the carina being much more 

 distinct in front. The color is as described above ; the spots of the elytra 

 are not disposed over the entire surface, there being a broad triangular 

 basal space entirely pale castaneous. 



Middle States, Illinois and Canada, rare. 



H. scabrosus, n. sp. 



Oblong oval, more narrowed in front, surface opaque, color piceous. 

 Head coarsely punctured and rugulose. Thorax twice broader than long, 

 sides moderately arcuate and slightly narrower in front, surface opaque 

 coarsely punctured and rugulose, and with a shallow broad impression 

 at middle of base and another on each side very indistinct. Elytra slightly 

 broader at base than thorax, sides gradually broader to middle then 

 gradually narrowed to apex, modei-ately but unevenly convex, sutural 

 region and fifth interval near apex, seventh interval at base and entire 

 marginal space more convex, surface striate, striae punctured, intervals 

 opaque, scabrous. Mesosternum simple, presternum with spiniform 

 crest in front. Body beneath and legs piceous, femora pubescent and 

 opaque at basal third only. Length .20-24 inch ; 5-6 mm. 



Somewhat variable in form and sculpture. Specimens before me from 

 Vancouver are less broad and so much smoother that almost all trace of 

 scabrous sculpture has disappeared from the elytra. The space between 

 the last stria and the margin is very convex, so that the margin is invisi- 

 ble from above. The sculpture of the species recalls that of Amphizoa, a 

 rather remarkable resemblance, as both occur in the same waters. 



Northern California, Oregon and A r ancouver. 



H, latus, n. sp. 



Broadly oval, slightly narrower in front, piceous black, moderately 



