888 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



Colynibetes gaudichaudi, its swimming legs being more slender and its hind coxse 

 having the front border less arched, it has scarcely any trace of lobing of the joints 

 of the hind tarsi, and the outline of its thorax and elytra are less perfectly 

 continuous than they are in C. gaudichaudi. 



The two species are found in western South America. 



I. 50.— Genus AGAMETRUS. ( Vide p. 547.) 



This aggregate comprises only three species ; the individuals possess a very 

 polished surface, and the outline of the thorax and elytra is very continuous, the 

 former is destitute of any raised margin at the side. 



The prosternal process is broad, flat and acuminate ; the epipleurae are quite 

 narrow behind the middle : the hind coxae are very large, and the wing of the 

 metasternum deflexed outside it is a very short, parallel sided, or linear band. The 

 coxal lines are quite absent. 



The genus is very closely allied to Leuronectes, but is well distinguished b}' the 

 absence of the coxal lines. 



The species are found in South America. 



I. 51.— Genus AGABINUS. {Vide p. 548.) 



This is an autogenus, comjjrising a single species, having quite the appearance of 

 one of the smaller, shining black Agabi. Coxal lines deeply impi'essed, nearly 

 straight ; the hind coxa small, its front border scarcely at all arched ; the coxal 

 border very distinct and continued forward till it meets the front border of the 

 coxa at nearly a right angle, the wings of the metasternum are large, and not 

 deflexed outside the coxa. Epipleura3 narrow behind the middle ( but still broader 

 than in Agabus). Swimming legs slender. Prosternal process rather broad, strongly 

 acuminate, its basal portion with a peculiarly thick margin, but its apical half quite 

 without margin. 



These characters are exhibited only by a single species ; it has a very polished 

 surface and is in appearance very similar to Agabus aubei, (Metronectes). The pecu- 

 liar structure of the coxal processes, gives it a superficial resemblance to Noterini, but 

 it has no real approximation thereto, and when the coxal processes are compared 

 with those of Dytiscus maculatus (Gen. Platambus) and with those of a member of 

 the Noterini, it is readily seen that even in this portion of the structure the relation- 

 ship is with the Platambus, and not with the Noterini: with Agabus pictipennis 

 (another member of Platambus found in Japan) the resemblance is still greater, and 

 the true position of the genus is demonstrated in an irrefragable manner by this 

 lattei- species. Although Agabinus has not the broad epipleurse of Platambus, still 

 it shows an approach thereto, for they are quite distinctly broader than in Agabu.s. 



