On Aquatic Carnivorous Coleoptera or Dytiscide. 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 haud sinuato, angulis posterioribus vix acutis, 
preesertim versus latera conspicue reticulato ; elytris nitidissimis, haud dense, obsole- 
tissime reticulatis, maculis lateralibus duabus inconspicuis, una pone medium, 
altera ad apicem, testaceis, punctis subseriatis minutis; thorace margine laterali 
nullo; prosterno processu lato, apice acuminato ; lineis coxalibus nullis. Long. 64, 
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 strize 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 posterioribus 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, preetereaque 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 
peruvianus (No. 776), itis 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 seepius conjunctis) 
testaceis; thorace eequali, undique subtiliter reticulato, basi utrinque sinuato, 
TRANS. ROY. DUB, SOC., N.S., VOL. I. 4B 
