On Aquatic Carnivorous Coleoptera or Dytiscide. 911 
head at the spot where the front part becomes free from the eyes, and therefore 
just behind the insertion of the antennz) 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 cox. The hind coxe are very 
large, but still their front border is separated by a not altogether short space from 
the middle coxe; the elongate deflexed wing 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 rather 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 legs are slender, their tibize have no spinules (or only very fine 
ones) on their lower face, their femora bear three or four sete of moderate length. 
The females have on the front and middle tarsi rather long erect sets 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 generic characters drawn from the absence of coxal lines and the nature of the 
setze 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 
region, 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 coxze. The hind coxe are extremely large, and their front border ap- 
proaches very near to the middle coxz ; 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 tibiz are 
