NORTH AMERICAN COLEOPTERA. 167 



LIMNOCHARIS Horn. 



The species of this genus are probably numerous in North 

 America, although but two have been described; I now add 

 several other peculiar forms. The genus is apparently valid, 

 since in all the numerous specimens which I have examined, 

 there are clearly eight ventral segments, the eighth being 

 small and more or less retractile, so that, while in the type 

 of angiistiila it is nearly as long as the seventh and very con- 

 spicuous, it may sometimes be almost entirely withdrawn; 

 it is never entirely invisible, however. The labrum also 

 differs greatly from that of Limnebius as described by La- 

 cordaire, for in Limnocharis it is not broadly rounded, but 

 is deeply sinuate in the middle. The antennae have, as 

 stated of Limnebius by Du Yal, nine joints, the first two 

 subanchylosed so as to form a long slender scape. 



The mentum instead of being strongly rounded, approaches 

 in Limnocharis more nearly the trapezoidal form, and in 

 the very singular L. co niciventris descvihed below, it is almost 

 perfectly trapezoidal, being transversely truncate at apex. 



The eighth segment: of the abdomen does not bear a tuft 

 of hair, but has one or two terminal sette, perhaps according 

 to the sex. 



The species of the genus at present known from the United 

 States are as follows: — 



Sides of the elytra distinctly arcuate. 

 Surface more or less polished. 



Prothorax very strongly transverse, at apex nearly twice as wide as 



long picea. 



Prothorax less strongly transverse, at apex less than one-half wider than 

 long. 



Apical angles of elytra narrowly biit distinctly rounded polita. 



Apical angles not rounded angUStula. 



Entire surface more or less alutaceous. 



Elytra at base slightly narrower than the prothorax; surface strongly 



alutaceous alutacea. 



Elytra at base equal in width to the prothorax; surface feebly aluta- 

 ceous; scutellum larger COngfener.. 



Sides of elytra strongly convergent, almost perfectly straight., conlciventrls.. 



