624 On Aquatic Carmvorous Coleoptera or Dytiscida. 
similar manner to the front feet, their claws are very unequal, the outer one being 
very thick and moderately long, twice the length and twice the thickness of the 
more arcuate inner one. In the female there is a distinctly reticulate area on the 
elytra in front of the middle towards each outside. 
Madagascar. 905. 
959. Rhantus validus, n. sp.—Ovalis, sat convexus, elongatus, nec latus, nitidus, 
fere levigatus, subtus nigricans, prosterno rufescente, supra testaceus, vertice nigro- 
variegato, thorace disco plaga parum discreta fusca, elytris nigro-irroratis, antennis 
pedibusque anterioribus rufis, pedibus posterioribus piceo-rufis: prothorace sine 
margine laterali ; tarsis posterioribus extus vix lobatis. Long. 153, lat. 8 m.m. 
The male has the front and middle tarsi a good deal incrassate and much com- 
pressed, and furnished beneath with long hairs, bearing narrow palettes, and the 
claws are moderately long, simple and equal. The female shows scarcely any 
greater development of sculpture than the male. 
South America, (Chili). 906. 
I. 68.—Genus COLYMBETES. 
Side pieces of fourth and following ventral segments very narrow ; metasternal 
groove narrow and indistinct; terminal joint of hind tarsus not longer than the 
preceding one. Wing-cases marked with transverse scratches, or (more rarely) 
smooth. , 
The eighteen species” of this genus are found in the northern parts of the Old 
and New Worlds: but one or two extend as far to the South-east as North- 
western Arabia. 
960. Colymbetes dahuricus, Aubé, Scutopterus dahuricus, M.C._—Ovalis, in medio 
dilatatus, convexus, niger, antennarum basi testaceo, clypeo rufo, vertice rufo- 
bimaculato, thorace elytrisque testaceis, his infuscatis margine pallidiori, illo in 
medio nigricante; corpore strigoso, strigis in elytris transversis, haud profundis ; 
elytrorum epipleuris in medio latioribus et magis elevatis. Long. 193, lat. 10 m.m. 
* The following species also no doubt belong to this genus, viz.—Colymbetes drewseni, Lec. (No. 1224 
huj. op.)? No. 967 var.; Greenland.—Colymbetes inzequalis, Horn, (No. 1232) near No. 963; North 
America.—Colymbetes simplex, Walk, (No. 1248)? near No. 975; Arabia. 
(No. 1251)!=No. 964; North America. 
North America.—whether Colymbetes includens, Walk. (No. 1233; Arabia) belong to the genus or not 
is doubtful. 
Colymbetes strigosus, Lec. 
Cymatonterus obscuratus, Mann. (No. 1284) near No. 961 ; 
