piceous, frequently tinged with rufous. The side margin of the prothorax is 

 sensibly twice as broad as in obtusatus, and by this means the two may be readily 

 separated. The reticulation of the upper surface is substantially as in obtusatus, 

 but the areolae are of slightly smaller average size. The male tarsi are a little 

 more incrassate, the protarsal claws slender, more elongate and less curved than 

 in obtusatus, and with a more pronounced angulation at the extreme base. Length 

 7.5 to 8.5 mm. 



Apparently an extremely local species, and aside from two examples 

 from Staten Island in the Roberts collection it is known to me only 

 from Marion, Mass., where on one occasion it was taken in some 

 numbers by Messrs Bowditch, Blanchard and the writer, in the nearly 

 dry bed of a small brook. 



It may be well to remember that planatus and obtusatus are the only 

 species of Agabus in our fauna having normally both postmedian and 

 apical yellow sub-marginal spots. In stridulator (semipunctatus auct.) 

 these spots are often seen, but the greater number of specimens 

 in my series show no trace of them. 



A. hypomelas Mann. Bull. Mosc. II, 1843, p. 221. 

 irregularis Mann. Bull. Mosc. Ill, 1853, p. 159. 



Oblong oval, piceous or brownish piceous, distinctly aenescent; head in front, 

 sides of thorax except at the hind angles, and sides of elytra, diffusely rufous; 

 beneath piceous ; antennae, mouth, epipleura and legs, rufous, the thighs in part 

 dusky. Head notably large, prothorax with sides rather straight, not quite as 

 wide at base as the base of the elytra, the outline therefore somewhat discon- 

 tinuous ; general form feebly obovate, the maximum width being at a little behind 

 the middle of the total length. Surface reticulation rather fine, the meshes un- 

 equal, and toward the sides and apex exhibiting a secondary system of minute 

 reticulation. The usual dorsal series of punctures are present on the elytra to- 

 gether with numerous minute punctules at the intersections of the reticulating 

 lines. In the male the four anterior tarsi are slightly thickened, but the glandular 

 hairs of the lower surface cover on the first joint only a small apical area. The 

 protarsal claws of the male are slender, equal, and absolutely simple, and seem 

 to be precisely alike in the sexes. Length 6.6 to 8.25 mm. 



Occurs along the North Pacific Coast from the Aleutian Islands to 

 British Columbia and Vancouver. 



A well characterized species which should be easily recognized, 

 but which often apparently is not, judging from the different names 

 under which it appears in collections. The species has no close allies 

 and does not fit in very smoothly anywhere. Because of a general 

 similarity in the form of the prosternal process Sharp placed it in his 

 Group 2 with seriatus and lugens, while stating that its "exact position 

 is not easy to define." Though of about the same width and convexity, 

 the prosternal process is rather shorter and less finely pointed 

 (acuminate) at tip than in seriatus and lungens, and the metasternal 

 cavity is correspondingly less developed. The restriction of the 



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