On Aquatic Canilvorous Coleoptera or DjtiscidcB. 845 



to the higher Dytiscidse (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 coxae to form a broad inter-coxal 

 process ; this meets the apex of the prosternal process but is not impressed with any 

 grove, uor does the apex of the prosternal process extend on to it. 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 cox*. The epimeron is 

 quite coveredbytheelytron,butondissection isfound to be quite the same as regards its 

 articulations and nearly the same in form as it is in the higher Dytiscidae (Cybister). 



The hind coxse 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 laminae 

 of these coxae 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 coxae, the second scarcely at all infringed on by the coxte, 

 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 coxae : 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 ciliae and setae, 

 there exists however a slender band of elongate ciliae placed in a groove on the outer 



6 Q J 



