On Aquatic Carnivorous Coleoptera or DytiscidcB. 837 



and beai'ing each a fine seta which does not project beyond the margin, these setse are 

 in some species more numerous and crowded together at the extremity and there 

 collected into a kind of depression on the face of the femur, but do not project beyond 

 its margin. The tarsus is a little longer than the tibia and is terminated by two 

 equal claws, the basal joint is about as long as the three following ones together. 



The species of this genus as yet known are peculiar to the European and 

 Mediterranean region with one in Japan. Noterus Irevis is the highest, Dytiscus 

 clavicornis the lowest species of the genus ; there is a very great difference between 

 the development of the swimming legs in these two forms : the former species shows 

 also the o-reatest development oi the sexual characters, and is remarkable also for 

 the accumulation of setce at the extremity of the hind femora ; in this latter respect 

 N. japonicus is intermediate between it and the other species. 



The genus presents a very interesting peculiarity, consisting in the development 

 of patches of dark colour, on the undersurface of the body and legs in the male sex 

 only. 



I. 7.— Genus COLPIUS. {Vide }x mi.) 



This is an isolated insect, of subhemispherical form, but nevertheless acuminate 

 behind : the surface is dull, the upper face covered witli a dense fine sculptui'e, the 

 lower with an extremely coarse irregular sculpture. The antennae are rather 

 slender and subserrate internally. 



The apical joint of the labial palpus is dilated and notched ; the prosternal process 

 is large, and broad, not truncate behind, but only very obtusely acuminate, it is 

 bordered by a raised margin, and is continued forwards quite on one plane, till at 

 the anterior margin of the prosternum it presents a vertical face ; the anterior 

 transverse band of the prosternum is small, the rather large coxoe being placed near 

 the front margin. The middle coxae are small and globose ; the metasternum seems 

 to be separated from the hind coxa by a nearly straight transverse suture, which 

 however is rendered extremely obscure by the coarse sculpture ; the coxal [jrocesse.s 

 are very broad, and become broader behind, but their outer angles are very little 

 produced backwards, the coxal cavities are separated by a rather broad space. The 

 epipleurae of the elytra are very broad at their basal portion, and continue distinct, 

 although narrow, till near the extremity of the body. The front legs are extremely 

 modified, and most peculiar : the femora are subcylindric and a little curved ; the 

 tibiae are articulated and shaped in such a manner that what should be the outer 

 edge is the lower one, and the inner edge is the upper one, the natural front face look- 

 ing outwards ; the upper edge is rounded and polished and terminates in an elongate, 

 stout, acuminate hook, this appears to be continuous with the tibia and the tarsus 

 has the appearance of being inserted at a distance from the extremity. The basal 

 joint of the tarsus is about as long as all the other joints together, and is in the 

 male much incrassate. The intermediate legs are feeble. The swimming legs are 



5 P 2 



