On Aquatic Carnivorous Coleoptera or Dytiscide. 537 
equal, and but little curved ; the reticulation of the upper surface is less obsolete 
in the female than in the male, the difference between the two sexes in this respect 
being more marked on the thorax than on the elytra. 
The species is very similar to Dytiscus serricornis, but is broader and flatter, has 
the thorax less elongate, the male front and middle tarsi remarkably dilated, and 
the hind legs of that sex simple. 
Eastern Siberia. 811. 
Group 23. 
Under-wings reduced to slips; sculpture of the elytra consisting of isolated 
scratches, of which the basal ones assume an oblique, the outer and apical ones a 
transverse direction. 
One North American species. 
757. Colymbetes bifarius, Kirby, Agabus bifarius, M.C.—Ovalis, sat convexus, 
niger, supra subzenescens, capite, prothoracis elytrorumque lateribus rufescentibus, 
antennis pedibusque rufis; elytris strigulis brevibus ad basin obliquis, apicem 
versus transversis, ornatis. Long. 6, lat. 32 m.m. 
The male has the basal joints of the front and middle tarsi distinctly dilated, and 
furnished beneath with moderately long hairs which bear distinct palettes, the 
claws of the front feet are rather elongate, very little curved, and scarcely sinuate. 
I have a male and female before me, and their sculpture is similar, except that the 
peculiar short scratches are rather more numerous and distinct in the female than 
in the male ; in two specimens from California (in bad condition), the sculpture of 
the female is different, the surface being opaque and the scratches on the basal 
part of the elytra are more elongate so as to form a reticulation : a third form, from 
Hudson’s Bay, differs from the Calitornian one by the scratches being much fewer. 
It is quite possible that these will prove to be distinct species. 
North America. (Canada, Hudson’s Bay, California). 766. 
I. 47.—Genus JL Y BIOSOMA. 
Hind coxz largely developed, with greatly arched upper border, so that the 
wings of the metasternum are very slender, paraliel-sided (or linear), but much 
curved ; swimming legs stout and short ; epipleuree behind the middle narrow. 
The unique species is found in North America. 
