856 Un Aquatic Carnivorous Culeoptera ur DyttscidcB. 



swiiuiiiing legs of the male are more powerful, as are also often all the other legs ; 

 the front and middle tarsi are frequently dilated ; these tarsi are also often compressed 

 laterally and rarely are quite flat on the upper surface : the anterior trochanters 

 in the male are frequently the seat of incomprehensible secondary sexual characters, 

 in aoiue species scarcely to be detected, while in others they ai'e carried to an 

 extent that may almost be called ludicrous. 



The peculiar structure of the front tarsi readily leads to any water-beetle 

 possessing it being identified as a member of this aggregate. In no other DytiscidaB 

 is the terminal joint of the front tarsus so little exserted from the third joint ; this 

 is so remarkable that in the females of some species of the genus the tarsi have the 

 appearance of being only three-jointed. 



The dark marks on the elytra are formed by lines placed in the longitudinal 

 direction, but of irregular lengths, and much united together in the transverse 

 direction so as to give somewhat the appearance of highly irregular transverse 

 bands ; the marks so formed rarely extend so far as the outer margin which is thus 

 nearly always paler than the sutural portions. 



The genus is in several respects approximated by Hyphoporus of the Hydroporini. 



Hyphydrus is distributed over the whole of the Eastern hemisphere, except the 

 colder parts thereof ; in the Western hemisphere it has only been found in New 

 Caledonia. 



I. 31.— Genus STERNOPRISCUS. {Vide p. 384.) 



Ten species form this aggregate ; their individuals are of small size, and of 

 moderately elongate form ; the punctuation of the upper and under surfaces is very 

 dense, and the colour more or less variegate. The sexual differences are often 

 extreme. The thorax has a longitudinal plica on each side. The prosternal process is 

 elongate and slender ; the middle cox« are absolutely contiguous, and their exserted 

 apices project beyond the level of the body ; the fork of the mesosternum is elongate, 

 and the prosternal process which extends over the middle coxse is thus rendered 

 peculiarly protuberant. The hind coxse are elongate externally. The hind coxal 

 cavities are not contiguous, but each has an internal prolongation, by means of 

 which the basal portions of the two swimming legs are allowed Yevy nearly to meet. 

 The coxal lines are short, but rather acutely elevated, distinctly turned outwards 

 near the apex, forming a rather acute coxal process, with a small coxal border. 

 The swimming legs are slender, their tibise are slender at the base, and near the 

 base have a crook or distortion, which is more conspicuous in the males than in the 

 females. The front and middle tarsi are distinctly five-jointed : the mesosternum 

 is placed at a very obtuse angle with the metasternum and thus is quite visible. 



The genus is very easily distinguished by the distinctly 5-jointed tarsi, and the 

 comparativelv ill-constructed and fitted together parts of the mesosternum and 

 adjacent pieces. It has points of similarity with widely separated forms, and has 



