On Aquatic Carnivorous Coleoptera or Dytiscide. 875 
which the few species found outside it have diverged : the other species known 
having been found in Africa and Mesopotamia. 
I. 44—Genus HYDROTRUPES. (Vide p. 492.) 
This is an autogenus, known at present only in a very imperfect manner. The 
form is rather convex above and flat beneath. Antenne short and stout, palpi very 
_ short, the labial ones excessively short and stout, the terminal joint being subquad- 
rate. Prosternal process short and flat, about as broad as long, strongly margined, 
metasternal impression short ; metasternum short, its sides with an abrupt 
deflexed slender termination ; hind coxee moderately developed, the coxal processes 
large, the coxal lines start from the apex of the metasternum and are at first 
approximate and parallel, but their terminal portions are much turned outwards, and 
do not reach the apex of the coxal processes ; these have a peculiar supra-articular 
border formed by a thickening of the edge of the process. Hind tarsi slender, 
(their joints not lobed,) of little use in swimming, terminated by two equal 
rather small curved claws. 
The above notes comprise all the information I can offer about this curious species, 
as I have not, when writing, the unique individual any longer at my disposition ; on 
the whole it would seem that Metronectes is the form to which it comes nearest, 
but this must be considered as being at present little better than a guess. 
It is said to have been found in California. 
I. 45.—Genus METRONECTES. (Vide p. 492.) 
This is an autogenus ; the form is rather depressed, but similar to that usual in 
Agabus, the base of the thorax being as broad as that of the elytra, the surface is 
polished and scarcely visibly reticulate ; the antennz and palpi are short and stout, 
and the last joint of the labial palpi is a good deal dilated ; the hind coxe are but 
little developed, being short, and their anterior border very little arched, the wings 
of the metasternum are comparatively large, the coxal lines and coxal border are 
almost entirely absent: the sides of the thorax are very distinctly margined ; the 
epipleuree behind the middle are a mere edge ; the prosternal process approaches a 
plane surface, and is finely margined; the swimming legs are feeble, their tarsi 
terminated by two curved equal claws. The sexual distinctions are very feeble: the 
male tarsi being very little incrassate, and the two basal joints furnished beneath 
with a very rudimentary sexual pubescence confined to a small area on the two 
basal joints, and the claws are quite short and simple like those of a female. 
This insect is readily distinguished from Agabus, by the absence of the coxal 
lines and the peculiar palpi; it recalls in some respects the South American 
Agametrus, but those insects have the hind coxe very large instead of very small 
TRANS. ROY. DUB. SOC., N.S., VOL. I, 5 U 
