On Aquatic Carnivorous Coleoptera or Dytiscide. 419 
Group 1. (Species 450 to 461). 
Swimming legs very slender, their tarsi slender and elongate, very distinctly 
longer than the tibiz ; the latter with the lower face densely punctured ; prosternal 
process narrow, carinate along the middle, often much compressed laterally, never 
quite flat, its form more or less obscured by fine setze ; elytra not denticulate near 
the apex ; surface of body very dull, the upper one bearing a more or less distinct 
bloom or tomentum, which is very easily removed by friction; the surface uni- 
colorous, or nearly so, always destitute of any definite marks or pattern ; sexual 
disparities in legs and feet scarcely to be detected, but often very remarkable as 
to the form of the prothorax. 
The species are about twelve in number, and are all found in clear running 
streams in the European and Mediterranean region. 
Group 2. (Species 462 and 463). 
Hind coxze distinctly separated by a partition projecting backwards beyond the 
coxal cavities; hind tibize densely and finely punctured on their infero-external 
aspect, but allowing the series of punctures near the edge to be seen; prosternal 
process remarkably broad and flat, without central carina ; colour of surface variegate. 
The species are only two in number; and both are European. 
Group 3. (Species 464). 
Hind tibie coarsely punctate on the infero-external face, with, however, the 
marginal series of punctures visible at the upper edge of the punctuation: hind 
coxal cavities not visibly separated ; elytra with a vague yellow pattern ; prosternal 
process not very broad and flat. This species is found in the Canary Islands. 
Group 4. (Species 465 to 494). 
Hind tibise with their infero-external face glabrous, and shining; hind coxal 
cavities not visibly separated, prosternal process neither large, nor broad and flat, 
elytra always variegate with yellow or red. 
This group comprises the greater number of the species of Deronectes, and they 
will be arranged according to whether the elytra have a minute sharp denticle 
near the extremity, or are without such denticle. This isnot a very good character 
as there are a few species in which the denticle is very obscure, and some others 
in which it is distinct in one sex, and less so in the other; if however a careful 
examination be made the observer will not have much difficulty in deciding to 
which of the two categories he should refer the individual under examination. 
A, elytra with a denticle near the extremity : species 465 to 484. 
B, elytra without a denticle near the extremity : species 485 to 494. 
TRANS, ROY. DUB SOC., N.S., VOL. II. 31 
