890 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



acute. The prosternal process is very broad, in one species, Agabus siuuatus, it is 

 quite flat and almost without margin, in A. jiictipennis the basal portion is coarsely 

 margined, while in the third species, D. maculatus, the middle portion of the pro- 

 cess is slightly convex, and the sides are again flattened out or explanate, and are 

 finely margined. In A. sinuatus the coxal lines are not so deep as in the othei- 

 species, and they are rather more divergent in front, and do not quite reach the 

 border of the coxa ; in this latter species the epipleurge are not quite so broad as in 

 the other two. 



The broad epipleurse are not found in other members of Agabides, but reappear 

 in Hj'derodes, and in Cybister in a variable manner. 



The geographical distribution is in Europe, Persia, and Japan. 



I. 53.— Genus ILYBIUS. [Vide p. 550.) 



This aggregate comprises twenty-four species, and is characterised by the 

 structure of the swimming tarsi which have their claws more or less unequal, and 

 the basal joints externally with the hind margin (more or less) distinctly lobed. 

 Prosternal process very compressed. Inner face of elytra with a tomentose area 

 at apex. Side of prothorax margined ; epipleurge narrow behind the middle. 



The species are generally of peculiar shape being distinctly convex longitudinally 

 as well as transversely, their sculpture is a reticulation of a fine and dense character 

 on the upper surface, and beneath they are finely strigose ; the colour is black and 

 pitchy red, and the onlj^ pale marks are a spot or dash near the side of the wing- 

 case, accompanied by another near the apex, and sometimes by a marginal yellow 

 band. 



The approximation made to Agabus is considerable and is at more than one 

 point. The lobing of the joints of the hind tarsi occurs slightly in some of the 

 species of the 19th group of Agabus, and the inequality of the hind claws of Ilybius 

 cinctus is very slight, and not greater than what is found in the male of Agabus 

 subtilis, a member of the group of the genus just mentioned. I. cinctus, however, 

 does not make any approach to any particular species of Agabus, and the approxi- 

 mation between it and Agabus subtilis is an approximation not of the species 

 themselves but of the two aggregates of which they respectively form a 

 portion. 



The lobing of the hind tarsi is greater in some .species of Platjaiectes than it is 

 in I. cinctus, but there is no approximation between these two in other respects. 



This lobing of the hind tarsi is really distinctive of the genus as compared with 

 Agabus, for it is greater in Ilybius cinctus (the species of the genus where it is 

 least) than it is in any species of Agabus. The inequality of the claws of the hind 

 tarsi is also really distinctive between the two aggregates, although as rec^ards 

 this the two actually touch by means of A. subtilis and I. cinctus. 



