On Aquatic Carnivorous Coleoptera or Dytiscide. 853 
species of the widely separated Sternopriscus, for instance, resemble greatly Bidessi 
in appearance, and possess similar swimming legs and even the peculiar plicee of 
the pronotum. 
The natural arrangement of the species I am unable at present to accomplish 
owing to the minute size of the creatures and the consequent fact that they have 
not been sufficiently collected, so that material for dissection of many of the more 
peculiar species cannot yet be obtained. It is probable that the aggregate as here 
defined will prove to consist of more than one distinct primary aggregate or genus. 
The best indications I can give at present on this point are the following remarks :— 
Nos. 242 and 243 are distinguished from all others by the fact that their headistruly 
and evenly margined ; an aproximation to Desmopachria is thus suggested and 
appears to be supported by some other details. ‘The rest of the species have not the 
front of the head margined, although many of them have a kind of waved transverse 
thickening near the front, giving the appearance at first sight of a real margin. 
Nos. 244, 245, and 246 no doubt form a distinct genus; although Iam not able 
to examine them thoroughly owing to having only a single individual of each. The 
form approximates to Hydrovatus being very acuminate behind, the size is very 
minute the head is not margined in front, the coxee and coxal cavities are formed 
much as in Desmopachria, while the prosternal process, depressed in the middle and 
carinate on each side, is like that of Dytiscus geminus ; hind tibize asin Bidessus. A 
comparison with 242 and 243, as well as with Hydroporus granarius, is highly 
desirable. The thoracic basal impression is smaller than in Bidessus and there is 
none on the elytra. 
Nos. 247 to 254 are insects of short broad form, without pubescence, with the 
punctures on the undersurface peculiarly large, and the sculpture on the upper 
surface also coarse, and the plica on the elytra remarkably developed, so that it 
assumes the form of an elongate carina extending for more than half the length of 
the wing-cases. It is in these species that the thickening across the front of the 
head above alluded to is most conspicuous. For one of them (Bidessus maculatus) 
Babington proposed the generic name Anodocheilus, which may ultimately prove 
of service, but at present the insect Babington had in view cannot be separated with 
advantage from the Old World Hydroporus porcatus, Klug, and Hydroporus 
bicarinatus, Clairv. 
Nos. 255 to 260, by their posterior coxee, which have a less extension in the 
longitudinal direction, are separated from the bulk of the aggregate, and by,this, 
and the coarser, more evenly distributed punctuation of their undersurface, as well 
as by the form of their front and middle tarsi, an approximation is made to some 
Hydropori; these species however are approached more or less closely by Dytiscus 
unistriatus and others that I have placed in the same group of the genus. 
The genus has a large distribution in both hemispheres, 
5 R 2 
