Un Aquatic Carnivorous Coleoptera or Dytiscidae. 853 



species of the widely separated Sternopriscus, for instance, resemble greatly Bi dessi 

 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 accomphsh 

 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 I am 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 coxae and coxal cavities are formed 

 much as in Desmopachria, while the prosternal process, depi-essed in the middle and 

 carinate on each side, is like that of Dytiscus geminus ; hind tibiae as in 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 coxse, 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 



