On Aquatic Carnivorous Coleoptera or Dytiscidce. 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 subfcucscens, capite, prothoracis elytrorumque lateribus rufescentibus, 

 antennis pedibusque rufis; elytris strigulis brevibus ad basin obliquis, apicem 

 versus transversis, ornatis. Long. 6, lat. 82 m.m. 



The male has the basal joints of the front and middle tarsi distinctly dilated, and 

 furnished beneath with modei-ately 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 Californian 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 ILYBIOSOMA. 



Hind coxas largely developed, with greatly arched upper border, so that the 

 wings of the metasternum are very slender, parallel-sided (or linear), but much 

 curved ; swimming legs stout and short ; epipleurse behind the middle narrow. 



The unique species is found in North America. 



