On Aquatic Carnivorous Coleoptera or Dytiscide. 943 
is very distinctly left exposed by the epipleura, while in other cases it cannot be 
at all perceived when the wing-cases are in the natural closed condition. The 
epipleuree show much variation in their width from species to species. The 
hind coxe are always very largely developed, and their upper border of the form 
already described. The coxal processes never have a large extension either in the 
longitudinal or transverse direction; the coxal lines are but little turned outwards 
near their termination, and they extend but a short distance in the anterior direction, 
so that they remain extremely remote from reaching the front border of the coxa, 
their extension forwards is however indicated by a curved series of punctures in 
front of the termination of the actual line. In the Australian genus Homeodytes 
the coxal lines are absent, and the coxal processes of rather unusual form. 
It is in this group of the Dytiscidz that the swimming legs attain their greatest 
and most admirable development ; the femora are very broad, and the tibize are 
often so thick and short that their length does not greatly exceed their breadth ; 
in Dytiscus reeselu actual measurement shows about 34 mn. of length, by 2§ m.m. 
of breadth. The superior of the two apical spurs is of slender form, and is 
more or less profoundly canaliculate along its inner face, and is either simply 
acuminate at the apex, or largely furcate there, or minutely tricuspidate; the 
inferior spur is dilated and flattened, but is quite acute at the apex, and is longer 
than, as well as broader than, the other. The tarsi are very thick and their hind 
margins though sinuate are not distinctly lobate-produced at their outer edges, 
and are destitute of fine ciliz. The claws are very variable; either there exists 
only a single thick, pointed, straight and immobile claw, or there are two, more 
slender, straight, equal claws, or the two claws may be unequal to a greater or 
less degree in length or thickness. It has been supposed that when there is only 
one claw present, it is because the two claws have become soldered and amalgamated 
into a single one; and as a groove may be detected running along the length of 
the claw this is cited as a relic of the original distinction into two claws: this is 
however quite erroneous. When there is only one claw present it is because the second 
claw is undeveloped or rudimentary ; this second claw in point of fact is present in 
all degrees of development ; and moreover where there are two well marked claws 
. present in the genus, each of the two claws may be seen to be deeply channelled 
(vide Cybister giganteus, No. 1,117) showing conclusively that the channel is not 
evidence of two claws being amalgamated. 
The Cybistrini are found in most parts of the world, except that they do not 
extend into the cooler regions, and must be considered as characteristic of the 
warmer and warm-temperate regions. The Australian species are uch more 
aberrant than those found in any other part of the world. 
