216 PROCEEDINGS OF THE ACADEMY OF 



has a large excavation each side ; the anterior angles are prominent, and the 

 base each side is sinuate. The superior epipleural margin is acute, but not 

 prominent, the margin of the elytra being thickened, and the marginal sulcus 

 somewhat remote from the extreme margin. The last ventral segment in 

 both sexes is transversely impressed each side, but in the male is deeply ex- 

 cavated and emarginate behind, the outline of the emargination being rounded 

 and not angular, They are all of a dull red color. 



6. G. c a v i c o 1 1 i s, obscure sanguineo-rufa, ovata convexa, thorace nitido, 

 brevi, lateribus subangulatis, angulis omnibus prominulis, basi utrinque pro- 

 funde oblique sinuato, disco cribratim punctato, profundo canaliculato, et 

 utrinque late excavato, elytris parce brevissime pubescentibus sat dense cribra- 

 tim punctatis ; antennis nigris, tarsis fuscis. Long. '21, 



One specimen from North Carolina, Dr. C. Zimmermann. This species must 

 be very similar to the European G. sanguine a, but I have had no oppor- 

 tunity for comparison. 



7. Gr. r uf os an gu i n ea Say, Journ. Acad. Nat. Sci., Phila., v. 299 ; ed. 

 Lee, ii. 343 ; Adimonia ruf. Lee, ibid. 344. 



Middle and Southern States. Of the same convex form as the preceding, 

 but not at all shining. 



8. G. h je m a t ic a, sanguineo-rufa, elongato- ovata, minus convexa, thorace 

 nitido, brevi, lateribus late rotundatis, angulis omnibus prominulis, basi 

 utrinque oblique sinuato, disco cribratim punctato, profunde canaliculato, et 

 utrinque valde excavato, elytris opacis, parce brevissime pubescentibus, con- 

 fertim fortiter punctatis, antennis nigris, pedibus nigris plus minusve rufo- 

 variis. Long -20 -22. 



Quebec, Canada, Mr. W. Couper ; also found in Illinois, and at Fort Liard, 

 Hudson Bay Territory. The last ventral segment of the male is deeply ex- 

 cavated, the excavation limited by a sharp edge, which is curved in front and 

 not angulated. 



Geoup III. 



Oval or elongate species, less convex than most of those of the preceding 

 groups, and clothed above with a fine sericeous pubescence ; the punctures are 

 never very coarse, the angles of the prothorax are frequently prominent, and 

 the marginal sulcus of the elytra is broader than usual, causing the margin 

 itself to appear thinner and more reflexed, except in G. tuberculata, 

 where the sulcus is somewhat separated from the margin, and the latter ia 

 slightly thickened, though much less so than in Group II. 



The species are found exclusively upon aquatic plants, and, with the ex- 

 ception of the small species allied to G. decora, are easily defined and re- 

 cognized. 



9. G. tuberculata Say, Journ. Acad. Nat. Sci. Phila., iii. 456 ; ed. Lee, 

 ii. 220; Adimonia tub., Lee, ibid. 



Middle and Western States ; distinguished by its larger size, and slightly 

 thickened elytral margin ; the sutural angle of the elytra is not prominent ; 

 the base of the thorax is obliquely sinuate near the sides. 



The fifth ventral segment in the male is narrowly incised at tip, and canali- 

 culate nearly to the base. 



10. G. punctipennis Mannh., Bull. Mose 1S43, 308. 



California, two specimens kindly sent me by Col. Motschulsky. Of the same 

 elongate form as the next species, with the front angles of the thorax scarcely 

 prominent, and with the sutural angle of the elytra equally prominent ; they 

 are, however, more finely punctured, and the punctures become smaller to- 

 wards the sides and tip. 



The fifth ventral segment of the male is acutely emarginate. 



[Oct. 



