NATURAL SCIENCES OF PHILADELPHIA. 523 



pale brown (sides of thorax more rounded than in C. exaratus). Russian 



America $ 17. dolabratus Payk. 



"56. Elongate oval ; thorax with extremely fine anastomosing rugosities, 

 sides almost straight ; lines of elytra moderate ; legs pale brown, thighs 

 slightly darker. Greenland $ 9 18. groenlandicus Aube. 



Sides of thorax strongly rounded, sinuate near the anterior angles, which 



are strongly acuminate. 



60. Elongate oval ; thorax feebly punctured towards the base, with scarcely 

 perceptible rugosities ; lines of elytra deep, moderately approximate ; legs pale 

 brown, thighs darker. Greenland 9 19. drewseni Lee* 



b. Elytra not striate transversely : Rantus Esch. 



Thorax pale, with two dark spots placed transversely : 



47. Elongate oval, elytra irrorated with black and pale ; presternum and 

 legs pale brown. Middle States and Canada. Col. maculicollis Aube. 



j 20. binotatus Harris. 



47. Elongate oval ; elytra irrorated with black and pale ; prosternum and 

 hind legs black, or very dark brown. Oregon and Russian America. 



21. d i v i s u s Aube". 



41. Elliptical, moderately convex; thorax pale yellow, with the front and 



hind margins broadly black; elytra irrorated with black and pale. Lake 



Superior, Canada, Hudson's Bay Territory, Oregon. . 22. a g i 1 i s Aube. 



B. Front and middle tarsi of male very slightly dilated : Colymbetes Clairv. 



50 - 53. Elliptical very slightly convex, above dark brown, shining ; sides 

 of thorax paler ; elytra with a subbasal transverse line, three narrow vittae on 

 each, and the lateral margin pale. Middle and Southern States. Dytiscus 

 calidus Fabr. ; Col. tceniolis Say ; Hydaticus meridionalis Mels. 



23. c a 1 i d u s Aube . 



Note on the Species of BRACHINUS inhabiting the United States. 

 BY JOHN L. LE CONTE, M. D. 



All the species of Brachinus found within our Territory are very similar in 

 color ; the head, thorax and legs are ferruginous, and the elytra are of a dark 

 blue, blackish, or greenish-blue color ; the under surface of the trunk, and 

 the 3d and following joints of the antennse, vary in color, according to species 

 and individuals, being sometimes nearly black, sometimes of the same color 

 as the head and thorax. The form and sculpture of the thorax differ very 

 much in the various species, and it is upon the characters derived from that 

 region of the body that I have relied principally in distinguishing the forms, 

 which I consider as entitled to rank as species, in the table given below. 



It may be alleged that the synoptic phrases are too short to enable the so- 

 called species to be recognized ; I can only say that as I have endeavored to 

 express the essential differences between the forms that I have recognized, 

 and as the forms, colors and sculpture, except as noted, are identical, any dila- 

 tation of the phrases would be mere surplusage. 



I must also add that I consider the species of this genus very decidedly 

 opinionative, and that I am only impelled to the publication of this note by 

 the necessity of giving names to a certain number of recognized forms, and 

 of placing as synonyms some which I formerly considered as distinct, but 

 which increased collections have since shewn to be varieties. 



* I have dedicated this very curious species to Mr. Chr. Drewsen, the distiuguishad entomologist 

 of Copenhagen, by whom it was sent to me, with several specimens ofC. groenlandicus. 



1862.] 



