550 On Aquatic Carnivorous Coleoptera or Dtjtiscidce. 



reticulatis, etiam ad apicem baud rugulosis, punctis seriatis magnis ; prosterni 

 processu lato fere piano, ad basin utrinque crassius marginato, sed baud conspicue 

 longitudinaliter depresso. Long. 7h lat. 41 m.m. 



Tbe tbree basal joints of tbe frotit and middle tarsi are scarcely incrassate in the 

 male, but are furnished beneath with moderately long glandular hairs, the claws 

 are slender and simple ; there seems to be no sexual difference in sculpture. 



The species is probably variable in colour, and is no doubt distinct from Dytiscus 

 maculatus, by its very polished surface, depressed form, and less sulcate prosternal 

 process : in this species also the coxal lines are more abruptly deflexed outwards 

 before the apex, so that the form of the coxal processes makes a greater approxi- 

 mation to what exists in Agabus. 



Japan. 836. 



I. 53.— Genus iZF^/t/'^'. 



Posterior tarsi externally with the hind margins of their joints not straight, but 

 lobate produced ; prosternal process very compressed laterally. 



This genus comprises twenty-four^' species peculiar to the Northern portions of 

 the Old and New Worlds ; they form two groups, viz: — 



Group ]. — Hind tarsi of the male with the joints externally margined at their 



lower edge, Nos. 781 to 794. 

 Group 2, — Hind tarsi of the male not margined at the lower edge externally, 

 Nos. 795 to 804. 



Group 1. 



781. Dytiscus ater, De Geer, Ilyhius ater, M.C — Ovalis, elongatus, convexus, nigri- 

 cans, subtus piceus, an tennis pedibusque quatuor anterioribus rufis, pedibus posterior i- 

 bus piceis; supra subopacus densius reticulatus, elytrisguttulisduabuspallidis; coxis 

 posterioribus evidenter reticulatis, margine anteriore extern e parum curvato. Long. 

 14, lat. 7i m. 



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

 incrassate and much compressed, and clothed beneath with long hairs, bearing 

 moderately large palettes ; on the front feet the anterior claw is thick, slightly 

 emarginate beneath, with the extremity sharp, the posterior one being not so thick 



* And in addition to these, the names in the following list probably refer to species of this genus. 

 Colymbetes fraterculu.s, Lee. (No. 1228) ; North America. — Colymbetes lateralis, Geb. (No. 1235); 

 Siberia. — Colymbetes picipes, Kirb. (No. 1244)? near No. 789 ; North America. — Colymbetes ungularis, 

 Lee. (No. 1256)? = No. 781; North America.— Ilybius badeni, Wehncke (No. 1470)? = No. 783; 

 Germany. — Ilybius kiesenwetteri, Wehncke (No. 1471) ; Germany. — Ilybius ovatus, Hoch. (No. 1472) ; 

 Kus:>ia. — Ilybius suffusus, Crotch (No. 1473); North America. 



