835 On Aquatic Carnivorous Coleoptera or Dytiscide. 
highly developed, the femora and tibie being broad ; their tarsi are moderately 
stout, quite as long as the tibiz, 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 margin, and not setigerous. ‘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 antenne, the broader 
swimming legs, the less developed anterior tibize, which, however, have a greater 
development of the apical spur, as well as by details of less importance. 
I. 6.—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 antenne 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 ; the front coxee 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 cilize, and its outer apical angle completely rounded 
off ; 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 beyond 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 coxz 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: the coxal cavitiesalmost quite contiguous. The swimming legs are ratherstout, 
the femora traversed by a series of punctures placed parallel with the hind margin, 
