On Aquatic Carnivorous Coleoptera or DytiscidcB. 911 



head at the spot where the front part becomes free from the eyes, and therefore 

 just beliind the insertion of the antennte) of the head is very reduced, and the eyes 

 are large and convex; the broad, short prosternal process is a good deal broader 

 than the width of the prosternum between the coxse. The hind coxce are very 

 large, but still their front border is separated by a not altogether short space from 

 the middle coxse: the elonsfate deflexed winof of the metasternum is somewhat 

 dilated towards the extremity. The coxal lines are obliterated ; traces of their 

 existence may be detected round the axilla, but on the coxal processes they are quite 

 absent so that there is no trace of a supra-articular border; the coxal processes have 

 no notch, but are marked by a ratlier conspicuous fovea ; the hind legs are highly 

 developed for swimming, being short and thick, and are terminated by two elongate, 

 but very unequal claws. The two terminal stigmata are transverse, and somewhat 

 large. The middle logs are slender, their tibite have no spinules (or only very fine 

 ones) on their lower face, their femora bear three or four setae of moderate length. 

 The females have on the front and middle tarsi rather long erect setre on their edges 

 beneath. The front tarsi of the male are only of moderate size, they are destitute 

 of fringing hairs, being surrounded only by distant spinules, the palettes of their 

 undersurface are of moderate size, the basal ones considerably, but not enormously 

 larger than the others : the middle tarsi are slightly incrassate at the base, and 

 bear round palettes beneath. The females are destitute of sexual sculpture. 



The genus seems a perfectly natural and homogenous one, as it stands at present; 

 the sfeneric characters drawn from the absence of coxal linos and the nature of the 

 setffi of the middle legs, being confirmed by numerous less conspicuous characters, 

 as well as by the sexual ones. 



It is distributed over a portion of the Earth's surface in tropical Eastern Asia, 

 Malasia, and Australia; it will probably prove specially characteristic of the Malayan 

 reo-ion, with species in the proximate portions of Asia and Australia. 



I. 73— Genus RHANTATICUS. {Vide p. 691.) 



The single species isolated under this generic name has the appearance of the 

 species of Rhantus, its individuals being of small size (a good deal less than ^ inch in 

 length) and of yellow colour, with the wing-cases speckled with black. The antennal 

 portion of the head is extremely reduced, the eyes large and convex ; the short and 

 broad prosternal process is a good deal broader than the width of the prosternum 

 between the coxce. The hind coxre are extremely large, and their front border ap- 

 proaches very near to the middle coxae ; the elongate deflexed wing of the meta- 

 sternum becomes slightly broader towards its termination ; the coxal lines are ob- 

 literated, and there is no supra-articular border; the coxal lobes have no coxal notch, 

 but a group on each of two or three punctures ; the hind legs are highly developed for 

 swimming, being short and stout ; the middle legs are slender, their tibiae are 



