834 On Aquatic Carnivorous Coleoptera or DytiscidcB. 



I. 3.— Genus HYBROCOPTUS. {Vide p. 2G1.) 



This aggregate is formed by five species ; the individuals are of quite small size^ 

 (only 2 m.m. long), oblong-elliptic, and transversely c(>nvex in form, without 

 pubescence and of a yellowish colour, with the elytra a little darker, and subject to 

 bein" marked with very indefinite large yellow patches, or vittse. Their antennae 

 are short and rather stout and very nearly simple, the middle joints being just 

 visibly broader than the others. The labial palpi are not dilated, although their 

 apical joint is just visibly thicker than the others. The prosternum in front of the 

 coxae is rather large, and along the middle is in one plane from the front to the 

 termination of the prosternal process ; this latter is small and narrow, its extremity 

 obtusely acuminate. The front tibife are moderately stout anrl bear a few Jong 

 spines or setae on the outer edge, and are armed at the apex with two distinct 

 spurs one of which is longer than the other and very slightly curved; the front 

 tarsi are simple and slender, and I believe without sexual difference : the hind 

 coxae at their insertions are very distinctly separated. The swimming legs are 

 slender, the hind margin of the femora furnished with a few distant short setse, which 

 scarcely extend to the apex ; the tibiae are slender; the tarsi slender, about as long 

 as the tibiae, terminated by the two small equal, curved claws. 



The species assembled under these characters may perhaps prove to form more 

 than one genus ; Nos. 8 to 10, have the hind coxal processes but little developed, 

 their outer apices being neither produced nor acute ; the other two species I have 

 only been able to examine very imperfectly ; H. bivittis has the coxal processes 

 more developed, so that their produced outer apices are very acute ; while H. 

 seriatus appears to be intermediate be' ween this latter species and the others in 

 this respect. 



As it stands, the genus is renresented in Australia, the Indo-Malay region, and 



Madagascar. 



The genus is interesting from the analogy it displays with Hydrovatus ; an 



analogy which evidently arises from the two being in an approximately similar 



stage of evolution. We have in Hydrocoptus, the characteristics of the higher 



.genus Noterus displayed in a far lower stage of evolution ; I liave not however 



associated the genus with Noterus in the second .synthesis, but have at present left 



it isolated ; it seems to me probable however that it is really connected with the 



Noterini, by Pronoterus as an intermediate form, and if so the genus will be 



correctly placed in the Noterini ; as however I have been unable to find any trace 



of a curved spur on the front tibia, and as this character is so prominent a feature 



of the other Xoterini, I have not associated Hydrocoptus with them at present. 



The name liydi-ocoptus has never hitherto received any definition, although it 



was proposed in ISoo, by Motschoulsky : in his Catalogue of Hydrocauthares de la 



Russie, he included under Hydrocoptus, the greater part of the European Hydro- 



pori; but in 1859, he described three species of the aggregate I am at present treating 



of under the generic name of Hydrocoptus (Etudes Ent. 1859, p. 43, 44) ; and I have 



