874 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



plane of direction of the prosternal process ; the anterior portion of the prosternum 

 not in the least thickened along the middle ; the anterior coxte rather prominent. 

 Prosternal process small, acuminate behind, connected with the very minute inter- 

 coxal process of the metasternum, which is not visibly impressed in front for its 

 reception : mesosternum not connected with inter-coxal process of the metasternum. 

 Hind coxae rather small, scarcely longer externally than along the mesial line, thoir 

 cavities not quite contiguous, the processes not quite contiguous, but forming 

 two divergent lobes having very little extension in the longitudinal direction- 

 Hind legs slender, their tibiae and tarsi elongate, the latter terminated by two 

 rather short equal claws. The maxillary palpi are short, the second and third 

 joints each but little longer than broad, fourth joint slightly swollen, pointed, quite 

 twice as long as the third joint. Labial palpi very short, last joint a little swollen, 

 acuminate, mentum without tooth in the middle. 



The form is rather parallel not very convex, the surface without pubescence, the 

 extremity acuminate with a projecting spine. 



This very interesting aggregate consists at present of three or or four obscure 

 species. The resemblance in appearance is rather to Celina than to any other known 

 form ; the tarsi are those of Agabini (but as yet the sexual distinctions are not 

 known) but the scutellum is covered (as in Hydroporini and Laccophilini), and the 

 co-adaptation of the base of the thorax and elytra is very complete. The head 

 shows no frontal suture at the sides, it terminates in front as an edge and the labrum 

 is exposed, the eyes are small. 



The genus must remain at present very isolated, its tarsi quite forbid an 

 association with the other families forming the aggregate Hydroporides, and it 

 cannot even be included as itself a separate member of that aggregate. One might 

 be tempted at first to consider it as only a primitive form of Agabini ; but careful 

 comparison with the other primitive forms of that aggregate (such as Agabus 

 cordatus and the allies) fails to indicate a relationship. Methles shows no trace of a 

 fruutal suture on each side of the head (as do the Agabini alluded to) ; its prosternum 

 is distinctly depressed between the front coxaa, and is more evidently placed on a 

 difl:erent plane to the prosternal process : the hind coxal cavities are not conjoined, 

 and the coxal processes and their lines have not the characteristics of the Agabini ; 

 again the base of the thorax and elytra are accurately co-adapted and the scutellum 

 concealed, a character quite foreign to the Agabini. 



The ofenus can therefore not be considered as belonging eitlier to Hydroporides 

 or Af'abini and can only be united in the synthesis that shall include both those 

 groups. 



It may perhaps be looked on as the remnants of a group which played a more 

 extensive and important part in the early history of the water beetles : of the few 

 individuals known, one comes from Madagascar, and it is quite possible that other 

 species may there be detected, and that this locality will prove to be a centre from 



