Oil Aquatic Carnivoivus Coleopiera or Dytiscidie. 879 



Group 3. 



Outline of thorax and elytra continuous, prosternal process very broad, polished 

 and flat, middle coxce rather widely separated, Avith highly developed metasternal 

 impression ; hind coxae rather well developed, the wings of the metasternum rather 

 short ; swimming legs moderately 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 

 coxae, 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, Lee, 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 coxae are of 

 moderate size. The clothing of the undersurface of the basal joints of the front 

 leet of the male is rather elongate, but does not show distinct palettes. 



Group 5. 



Prosternal process broad and polished ; its margin just behind the coxae 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 coxte 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 laciniae 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 coxse, polished, gently convex trans • 

 versely, not at all compressed, very finely margined throughout ; hind coxse well 



