On Aquatic Carnivorous Coleoptera or DytiscidcB. 547 



I. 50.— Genus AGAMETRUS. 



Side of prothorax without raised margin ; coxal lines absent. 

 The three species are all South American. 



774. Agametrus labratus, n. sp. — Ovalis, sat latus, subdepressus, niger, antennis 

 pedibusque rufis, capite anterius prothoraceque ad angulos anteriores late rufes- 

 centibus; thorace basi utrinque baud sinuato, angulis posteriorlbus vix acutis, 

 prsesertira versus latera conspicue reticulato ; elytris nitidissimis, baud dense, obsole- 

 tissime reticulatis, maculis lateralibus duabus inconspicuis, una pone medium, 

 altera ad apicem, testaceis, punctis subseriatis minutis ; thorace margine lateral! 

 nullo ; prosterno processu lato, apice acuminato ; lineis coxalibus nuUis. Long. 6i, 

 lat. 3| m.m. 



The male has the basal joints of the front and middle tarsi scarcely incrassate 

 and furnished beneath with glandular hairs : the apical ventral segment has a few 

 oblique striee on each side the middle : there is no sexual difference in the sculpture 

 of the upper surface. 



South America, (Venezuela). 823, 



775. Agametrus humilis, n. sp. — Ovalis, sat latus, niger, antennis pedibusque 

 rufis, capite anterius prothoraceque ad latera late rufescentibus ; thorace basi 

 utrinque subsinuato, angulis posteriorlbus sat acutis, undique subtiliter reticulato, 

 basi utrinque versus angulos posteriores subimpresso ; elytris nitidissimis, crebrius 

 obsoletissime reticulatis, maculis lateralibus duabus, una pone medium, altera ad 

 apicem, testaceis, prsetereaque linea externa apicali subdistincta ; thorace margine 

 laterali nullo ; prosterni processu lato, apice acuminato ; lineis coxalibus nullis. 

 Long. 7, lat. 4 m.m. 



This species is about intermediate between A. labratus, and Colymbetes 

 peruvianas (No. 776), it is distinguished from the former, by the less distinct reticula- 

 tion of the thorax, and its more acute posterior angles, and closer reticulation of 

 the elytra. I have seen only females. 



South America, (Venezuela). 824. 



776. Colymbetes peruvianus, Cast., Copelatus peruvianus, M.C. — Ovalis, sat latus, 

 subdepressus, nitidus, niger, antennis pedibusque rufis, thorace ad angulos anteriores 

 elytrisque maculis duabus conspicuis (a linea subobsoleta saepius conjunctis) 

 testaceis; thorace aequali, undique subtiliter reticulato, basi utrinque sinuato. 



TBANS. ROT. DOB. SOC, U.S., VOL. 



4 B 



