860 On Aquatic Carnivorous Coleoptera or Dytiscide. 
Ceelambus, from which it differs by the terminal joints of the front tarsi, and by 
the greater separation of the articulations of the swimming legs. 
The species are found in the East, in India, and Egypt. The genus is not a very 
natural or satisfactory one, as Hydroporus solieri is not so Hyphydroid as its allies; 
there can be little doubt that other allied species remain to be discovered, and the 
separation of the species into two distinct aggregates would be at present premature. 
I. 33.—Genus PAROSTER. (Vide p. 391.) 
Three species from Australia form this aggregate; the individuals resemble 
greatly ordinary Hydropori, but have the upper surface more convex transversely 
than is usual in the species of the genus Hydroporus: the size is rather small, 
(3 or 4 m.m. of length) the form convex, rather short, but not very broad; the 
surface is without pubescence. The head is not in the least margined in front; 
the prosternal process is compressed laterally, strongly carinate, and elevate along 
the middle; the mesosternum does not connect with the inter-coxal process of the 
metasternum ; the hind coxe have a moderate extension in the anterior direction ; 
their processes are peculiar, the intra-rimal portion being prolonged considerably 
beyond the extra-rimal portion ; the coxal lines are effaced in their posterior part, 
the coxal border is excessively minute with slender, acute, outer angle, and the 
articular cavities are much exposed; the structure of these parts may be briefly 
described by saying, that the articular cavities are rather widely separated, and 
that there exists a quite distinct, indeed rather large coxal notch, notwithstanding 
the small size of the terminal portions of the coxal processes. The hind legs are 
slender, their tibiz are slender as well as a little crooked below the knee; the 
genicular area of the wing-case is bordered behind by a raised line ; the inner face 
of the wing-case is without any trace of apical ligula: the basal ventral segment 
is not soldered to the coxre. 
The species are peculiar to Australia and are very rare in collections at 
_ present. 
These obscure and unattractive insects prove to be of considerable interest when 
examined and compared, and to be much isolated: they have resemblances to 
Bidessus (of the Bidessini), as well as to Coelambus of the Hydroporini; the 
approximation to Bidessus consists in the form of the articular portions of the hind 
coxee, which may be described as that which exists in Bidessus but rendered more 
conspicuous by the wider separation of the articular cavities: the slender hind 
tibia also are such as exist in Bidessus. The genus differs from Celambus by 
the peculiarities of the coxal processes, and by the want of ligula on the inner 
face of the wing-case. 
