Sept., I9I2.] Matheson : Haliplid.e of North America. 161 



A. Terminal joint of palpi small, subulate, shorter than the preceding. Pos- 

 terior coxa; concealing only the first three segments of abdomen. 

 B. Pronotum quadrate, widest in front of the middle ; two lateral basal 

 impressions present extending more than half the length of the 

 pronotum. Fourth tarsal segment scarcely shorter than the first. 



Brychhts Thomson. 



BB. Pronotum strongly narrowed and truncate in front, widest at the 



base, above strongly convex. Fourth tarsal segment much shorter 



than the first Haliplus Latreille. 



AA. Terminal joint of palpi large, conical, longer than the preceding. Pos- 

 terior coxse concealing all but the last segment of abdomen. Pronotum 

 strongly narrowed and truncate in front, convex above. Fourth tarsal 

 segment shorter than the first Peltodytes Regimbart. 



BRYCHIUS Thomson. 



Brychius Thomson, C. G. Skand. Col. II, 1859, p. 8. 



Type. — Dytiscus elevatus Panz. Fn. Germ., XIV, p. 9. 



The gentis Brychius is easily distingtiished from the other two 

 genera throtigh the quadrate form of the pronotum and the narrow, 

 more elongate form of the body. The sides of the pronotum are sin- 

 uate, widest just in front of the middle. Well marked basal impres- 

 sions (striola of some authors) are present, reaching beyond the 

 middle of the pronotum. The elytra are marked with ten rows of 

 punctures. The tarsi are five segmented, long and slender. The 

 claws are long. 



The genus contains five European and one North American spe- 

 cies. So far as known they all live in running water. 



Brychius hornii Crotch. 



Brychius hornii Crotch. Trans. Amer. Ent. Soc, IV, 1873, p. 383. 



General color pale yellow with black markings on elytra. Length 

 3.5-4 mm. 



Head pale yellow, punctate ; antennae yellowish ; labrum emarginate, 

 rounded at the sides, a row of small setae on the anterior margin. 



Pronotum quadrate, the lateral margins sinuate, basal impression present 

 and exceeding one half the length of pronotum, punctate, the disc smooth. 

 Prosternal ridge margined, not grooved, convex laterally and longitudinally, 

 punctate, sharply declivous in front, the sides constricted in the region of the 

 prothoracic legs, widening anteriorly. Legs yellowish, posterior coxae punctate, 

 rounded behind, not reaching the fourth segment of abdomen. Abdominal 

 segments shining, punctate. 



Elytra yellowish with ten rows of black punctures, intervals rarely punc- 

 tate. Posterior half of the margins of the elytra denticulate. 



