On Aquatic Carnivorous Coleoptera or Dytiscide. 845 
to the higher Dytiscidee (such as Cybister), with the exception that the fork by 
which it terminates below is but little developed. 
The sternal pieces of the metathorax are rather large and have more than twice 
the area of the corresponding pieces of the mesothorax. The metasternum 
projects in the middle in front between the middle coxee to form a broad inter-coxal 
process ; this meets the apex of the prosternal process but is not impressed with any 
grove, nor does the apex of the prosternal process extend on toit. At the hind border 
in the middle there is a short transverse suture. The episterna are narrow behind, 
but in front are prolonged inwards so as to touch the middle coxre. The epimeron is 
quite covered by the ely tron, but on dissection isfound to be quitethe same as regards its 
articulations and nearly the same in form as it is in the higher Dytiscide ((ybister). 
The hind coxz are rather large, and have fully one-half of the area of the meta- 
sternal pieces ; they are separated in front from the metasternum by an approximately 
straight, or directly transverse, suture; this suture is however slightly undulated 
and its nearest approximation to the middle coxa is at a point which is considerably 
nearer to the mesial line of the body than it is to the epipleura; the internal laminze 
_ of these coxe are large and are closely applied to one another along the mesial line, 
externally each is separated in an abrupt manner from the outer or femoral lamina, 
and the line of separation is in front much directed outwards, and does not reach 
the metasternum, it is not marked by any definite impressed line so that there is 
no true coxal border, the articular cavities are widely separated, and terminate 
internally in such a manner as to form a short broad notch. 
Hind-body with six visible horny, ventral segments ; the first one interrupted in 
the middle by the hind coxz, the second scarcely at all infringed on by the coxa, 
but with its middle part distinctly prolonged forwards, so as to form an obtuse 
triangle adapted to the apex of the articular portions of the hind coxe: the ventral 
sutures are all distinct. 
The scutellum is large, and exposed at the base of the elytra. 
The wing-case has a well developed epipleura, which is very broad at the base 
but becomes greatly narrower at the side of the first ventral segment, and continues 
rather narrow till the commencement of the last segment, where it disappears ; this 
epipleura is very much inflexed, and very closely embraces (or is coadapted with) 
the flanks of the undersurface of the body: at the base of the wing-case, on its inner 
face, there is a free scutellar membrane. 
The ventral segments have a lateral border, which is clearly divided into two 
portions, each of which is horny, the upper portion on each segment is about equal 
in width to the lower, and the pieces on the successive segments from base to 
extremity continue of about one width, except that on the terminal segment the 
lateral pieces disappear from the posterior half of the side of the segment. 
All the legs are elongate and slender, and peculiarly free from ciliz and sete, 
there exists however a slender band of elongate cilize placed in a groove on the outer 
5Q23 
