83(3 On Aquatic Carnivorous Coleoptera or Dijtiscidce. 



highly developed, the femora and tibiae being broad ; their tarsi are moderately 

 stout, quite as long as the tibiae, the basal joint as long as the three following ones 

 together ; the femora on their lower face are marked with a series of punctures, 

 very distant from the hind mai-gin, and not setii^erous. The middle legs also are 

 broad. 



So far as yet known the genus is confined to Madagascar and tropical Africa. 



I have only been able to study it in a very imperfect manner, but it appears to 

 me very distinct from Noterus, by the simple slender antennae, the broader 

 swimming legs, the less developed anterior tibiae, which, however, have a greater 

 development of the apical spur, as well as by details of less importance. 



I. G.— Genus NOTERUS. {Vide p. 265.) 



The six species composing this aggregate have a peculiar facies, being transversely 

 convex above, flat beneath, and much narrower behind than in front ; they have an 

 extremely polished surface, with a greater or less development of isolated punctures 

 towards the posterior part of the elytra. The antennae are liable to extreme and 

 extraordinary sexual developments ; in the female they are moderately stout, with 

 one or more of the middle joints slightly broader than the others, while in the male 

 they are more or less incrassate, and one or more of the middle joints become 

 extremely developed and of strange form. The last joint of the labial palpus is 

 dilated and notched. The prosternal process is moderately broad, with its apex 

 obtuse I the front coxae are placed at a considerable distance from the front of the 

 prosternum. The front legs show great sexual differences ; in the females the 

 anterior femora have a slight curved emargination on the front of the lower margin 

 of the femur; in the male this notch is much larger. The tibia has its outer 

 margin densely set with short ciliae, and its outer apical angle completely rounded 

 ofi^ ; in the male the tibia is broader than in the female, and its inner margin bears 

 a large angular prominence near the extremity ; the tarsus is inserted in a large 

 cavity on the posterior face of the tibia, and from this spring two spurs, one placed 

 near the inner margin scarcely projects beyond the apex of the tibia and easily 

 escapes observation, the other one is much longer, and is gently curved, and it is 

 directed somewhat towards the outer margin and projects much bej'ond the tibia, 

 being usually closely applied to the inner edge of the basal joint of the tarsus. In 

 the female the basal joint of the tarsus is stout, and as long as the three following 

 joints together : in the male it is extremely large and incrassate. The suture 

 between the hind coxae and the metasternum is quite distinct, and nearly attains 

 the middle coxal cavity. 



The coxal processes are largely developed, and a good deal prolonged at the outer 

 angles : thccoxal cavities almost quite contiguous. The swimming legs are ratherstout, 

 the femora traversed by a series of punctures placed parallel with the hind margin. 



