A. bicolor Kby. Faun. Bor. Am. IV, 1837, p. 70. 

 mutus Shp. On Dytiscidae, 1882, p. 513. 



Very close to phaeopterus in size, sculpture and structure, but easily separated by 

 its color as indicated in the table. The coxal plates are large, the distance be- 

 tween them and the middle coxal cavities being even a little less than in phaeop- 

 ierus, and quite evidently less than in subfuscatus. In some examples there is a 

 fairly well developed series of punctures along the inner margin of the hind 

 tibiae, these being almost or quite lacking in all specimens of phaeopterus exam- 

 ined, but the character is a variable one and must be used with caution. Length 

 6.8 to 8 mm. 



Kirby described bicolor from a single specimen taken in British 

 America "in latitude 54." I have not seen the type, but the descrip- 

 tion, so far as it goes, agrees so well with Sharp's mutus, described 

 from Hudson's Bay, that I requested Mr. Arrow to carefully compare 

 the two types. He has done this and writes me that they appear 

 to be in all respects identical. For a cotype of mutus from the Sharp 

 collection I am indebted to Mr. Arrow ; there is also before me an 

 example taken by Mr. Wallis at Mile 214 Hudson Bay R. R. and three 

 examples (Sherman collection) collected by Mr. F. S. Carr at Edmon- 

 ton, Alberta, which seem to be the same thing. 



A. confinis Gyll. Insecta Suecica I, 1808, p. 511. 



ovoidcus Cr. Tr. Am. Ent. Soc. IV, 1873, p. 418. 

 longulus Lee. Proc. Am. Phil. Soc. XVII, 1878, p. 596. 



This Northern European species seems to be rather rare with us and I have seen 

 but few specimens in our collections. The color is of the congener type, the very 

 minute and regular elytral reticulation and extremely fine punctulation are nearly 

 as in the four preceding species. The size is greater than in any of its nearer 

 allies, but the species is most readily recognized by the form of the prosternal 

 process, which is strongly laterally compressed so as to be acutely carinate along 

 the middle. Infuscatus possesses nearly the same structure, but is readily sep- 

 arated by the rugose intralinear area of the hind coxae, as well as its smaller size 

 and commonly fusco-irrorate elytra. Length 8.8 to 9 mm. 



This species occurs in the latitude of our Canadian border. The 

 three examples before me bear labels, Bayfield, Wisconsin (Wickham) 

 and Duluth, Minnesota. LeConte's type of longulus, from Lake 

 Superior, is absolutely identical. 



A. infuscatus Aube, Spec. Gen. 1838, p. 330. 



The acutely carinate prosternal process, and rugose intralinear area of the hind 

 coxae, taken together, are sufficient for the identification of this species. The 

 color is in general of the congener type, but the elytra are of a rather duller 

 brownish yellow or brownish gray, with the infuscation very often taking the 

 form of a dense irroration or nebulosity such as is rather frequently seen in 

 lutosus, and occasionally elsewhere. The sides of the thorax are pale in all 

 specimens seen. The elytral reticulation is minute and very regular and without 

 fine punctulation. The male protarsi are quite strongly incrassate, the protarsal 



2 9 



