On Aquatic Carnivorous Coleoptera or Dytiscide. 931 
tropical South America, the Pacific Islands (including New Caledonia) or the 
Malayan and tropical Asiatic regions. The one or two species found in New Zea- 
land are very closely allied to Australian species. Australia (with Tasmania) 
possesses five genera (containing about thirty species) peculiar to itself, but the 
great majority of the species are found in the North American and European regions, 
where the three genera Coelambus, Deronectes, and Hydroporus are represented 
by about 260 species. No member of the group has yet been found in Japan, 
so that in this respect Japan and tropical Asia agree, and are very different from 
Europe. 
II. 10.—Group Agasini. (Vide p. 491.) 
This aggregate of the second degree is formed by ten primary aggregates which 
include one hundred and forty-four species. The size of the individuals varies from 
6 m.m, to 14 mm. of length, so that in the stature of the individuals the group 
‘stands at about the central point of the Dytiscidee. 
The upper surface is very rarely indeed possessed of a true punctuation, its place 
being taken by a reticulation of fine scratches, forming meshes of various shapes 
and magnitudes, according to the species ; sometimes this sculpture becomes exces- 
sively fine, and occasionally the surface is smooth and polished. The colour is 
usuaily obscure, or dark with a brassy tint ; few species are variegate. 
The characters of the group are that the semimembranous piece bordering the 
inner edge of the first ventral segment is smooth, and not thrown into transverse 
folds as it is in the Colymbetini; the apex of the wing of the metasternum reaches, 
when the wing-cases are closed, to the edge of the epipleura ; the hind femur bears 
on its undersurface, at the extremity and quite close to the hind margin, a more or 
less developed group of cilize ; and the side piece of the fourth and of the following 
ventral segments is comparatively broad. 
The first of these characters is merely a negative one, and by it-the Agabini 
depart from the Colymbetini to agree with the vast majority of the Dytiscide. 
The character drawn from the relation of the points of the metasternal wings to 
the epipleurze is of little consequence, and moreover is not absolute but is rather 
one of degree: it depends on the fact that the metathoracic episternum (placed at 
the antero-external portion of the metasternum) proceeds backwards between the 
edge of the wing-case and the wing of the metasternum till 1t terminates as a sharp 
point, contiguous with the point of the metasternal wing; this character however 
is not absolute, for in Dytiscus ater (No. 781) the exposed terminal portion of the 
episternum is not a sharp point, but is truncate; the point of the metasternal 
wing in that species does not therefore reach absolutely so far as the epipleura, 
although it approaches very near indeed thereto. 
In those species of the aggregate that have the swimming legs but little developed, 
the femoral cilize are, like the legs themselves, less highly developed and perfect : 
TRANS. ROY, DUB. SOC., N.S., VOL. I. 6 D 
