874 On Aquatic Carnivorous Coleoptera or Dytiscide. 
plane of direction of the prosternal process ; the anterior portion of the prosternum 
not in the least thickened along the middle; the anterior coxe 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 coxe rather small, scarcely longer externally than along the mesial line, their 
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 tibize 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 shghtly swollen, pointed, quite 
twice as long as the third joimt. 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 
frontal suture on each side of the head (as do the Agabini alluded to) ; its prosternum 
is distinctly depressed between the front coxa, and is more evidently placed on a 
different 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 Agabin1 ; 
again the base of the thorax and elytra are accurately co-adapted and the scutellum 
concealed, a character quite foreign to the Agabini. 
The genus can therefore not be considered as belonging either to Hydroporides 
or Agabini 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 
