On Aquatic Carniverous Coleoptera or Dytiscide. 879 
Gepovur 3. 
Outline of thorax and elytra continuous, prosternal process very broad, polished 
and flat, middle coxze rather widely separated, with highly developed metasternal 
impression ; hind coxz rather well developed, the wings of the metasternum rather 
short ; swimming legs mcderately slender. 
These species differ from the more highly developed of the members of group 2 
by the broader metasternal impression, and by a better development of the hind 
cox, which encroach more on the wings of the metasternum, so that these are 
shorter. The other characters therefore are those mentioned as distinguishing the 
second group. 
Agabus brevicollis, Lec., is only placed provisionally in this group, for I have 
seen but a single badly preserved individual: its prosternal process is elongate, and 
therefore appears comparatively narrow. 
Group 4. 
The characters of this species are similar to those of the highly developed members 
of group 2, but the swimming legs are highly developed, being thick and short. 
The species must be considered as one of the most perfect of the Agabi: the 
outline is very continuous, the surface polished ; the prosternum is carinate-elevate 
along the middle, its process broad and flat and powerful. The hind coxe are of 
moderate size. The clothing of the undersurface of the basal joints of the front 
feet of the male is rather elongate, but does not show distinct palettes. 
Group 5. 
Prosternal process broad and polished ; its margin just behind the coxze very 
broad and dilated, in the posterior half excessively fine. 
The three species associated by the above character form a natural group ; they 
are of perfect form with continuous outline, their hind coxe are largely developed, so 
that the metasternal wings are rather short, the hind femora are largely developed; 
especially distinct is the lamina at the postero-external angle. The coxal processes 
are broad, and subtruncate at their common extremity, the notch between them 
being but short. In Colymbetes stagninus, the laciniz of the metasternum are 
rather longer than in the other two species; in Agabus texanus, the coxal processes 
are not so extremely truncate at the apices. 
Group 6. 
Thorax and elytra very coadapted and continuous in outline ; prosternal process 
rather narrow, very little dilated behind the coxe, polished, gently convex trans- 
versely, not at all compressed, very finely margined throughout; hind coxe well 
