On Aquatic Carmvorous Coleoptera or Dytiscide. 867 
Group 2. 
Two closely allied species form the second group of Deronectes ; the form of the 
body is peculiar; the elytra have their terminal portion more prolonged and 
acuminate, and the last ventral segment is more elongate than in the members of 
the following group. The other characters of the group have been given on p. 419, 
and it is only necessary here to remark that as the first eroup of the genus agrees 
with this second group in the separation of the hind articular cavities; and as H. 
tessellatus, (the third group), has the posterior tibize punctured in a similar manner, 
it is clear that these characters do not justify the establishment of a distinct genus 
for the second group: I expect however that characters will ultimately be detected 
that will call for its separation as a good and distinct aggregate. 
Group 8. 
This group consists of an isolated species, with coarsely punctate hind tibiz, but 
in other respects similar to the following or fourth group; it would thus seem to 
be a connecting link between the first and fourth groups, but such is not really 
the case, and it is more correctly an insect belonging to the fourth group but 
possessing to a considerable extent one of the more important characters of the 
first group. It is to be noted that this exceptional species is an insular one, found 
in the Canary Islands, and it is additionally interesting to find that the H. vigilans of 
Madeira which I have placed in the following groups, has some punctures placed 
on the basal portion of the tibia and so forms a connecting link between the H. 
tessellatus and the fourth group. 
Group 4. 
The fourth group of Deronectes comprises the majority of the genus, and 
includes all the species having the infero-external face of the hind tibize glabrous 
and shining. The group is specially well represented in the regions near the 
Mediterranean, but includes a very widely distributed alpine and boreal species, 
apd one or two from the New World. 
About fifty species, arranged in four groups as above expressed, form the aggregate 
Deronectes. The form of the individuals is oval, or oblong oval, and only moderately 
convex beneath, the upper surface is very finely pubescent, and finely punctate. 
(In most of the species, the punctuation is very fine, and the undersurface is 
entirely without coarse punctures, but has an extremely dense, fine, somewhat 
rugose sculpture, rendering it very opaque, and the upper surface is more or less 
variegate in colour; the remarkable first group forms however an exception in these 
respects, for the surface is not variegate, and a coarse punctuation exists, to a greater 
or less extent, in combination with the fine sculpture). 
The head is never margined in front, the epipleure of the elytra are much narrowed 
TRANS. ROY. DUB. SOC., N.S., VOL. II. 6 T 
