On Aquatic Carnivorous Coleoptera or DytiscidcB. 897 



borders of the coxee ; on reaching the coxal process they are rather gently directed 

 outwards, and leave the coxal lobe large and broad with a narrow supra-articular 

 border ; the separation behind of the two coxal lobes is but slight, and they show- 

 only the very slightest trace of a coxal notch. The hind legs are rather powerful 

 and well developed, the femora have a well marked lamina at the apex, with a 

 sharply defined rectangular angle, and no trace of setae : their tarsi have the lower 

 portions of the hind margins strongly lobed externally, and are terminated by two 

 nearly straight closely applied claws, that are about equal to one another in length 

 but the inner one is considerably stouter than the other. The apices of the elytra 

 are slightly obliquely truncate. 



The position of the genus is decided in a positive manner by Rhantus marginatus 

 in Lancetes (No. 917, Coptotomus argentinus, Reiche) ; although clearly allied to 

 Coptotomus, this however differs strikingly from it in the form of the coxal lobes ; 

 these in Coptotomus are similar to what exists in Ilybius, whereas in the 

 genus Lancetes the approximation in structure of the coxal lobes is to the very 

 different form found in Dytiscus. The peculiar form of the prosternum is not so 

 different to that of Lancetes, but may be defined as an exaggeration of the Lancetes 

 prosternum after the manner of Cybister. 



The species are, so far as yet known, confined to the United States of North 

 America. 



I. 60.— Genus LANCETES. { Vide p. 602.) 



The five species associated to form this aggregate, consist of insects of rather 

 large size for the Agabini (about 10 m.m. or over in length), they are of more or 

 less narrow form, and their colour is a variegate mixture of black and yellow, or 

 yellowish red, and they have very little sculpture ; their appearance is greatly 

 that of the species of Rhantus. The elytra are distinctly sinuate-truncate at the 

 extremity, the coxal lobes elongate, and deeply separated from one another. The 

 colour is a variegate mixture of black and yellow, or yellowish red, and they have 

 very little sculpture. The prothorax is margined at the sides ; the palpi have the 

 apical Joint only slightly or not at all incrassate, and with faint indications of an 

 apical notch : the prosternum is thickened along the middle, but is not vertical in 

 front ; the prosternal process is elongate and acuminate and received into a well 

 developed cavity on the inter-coxal process of the metasternum. The hind coxae 

 are moderately large, but the side wings of the metasternum are also large, and 

 not deflexed outside the coxse. The coxal processes are very peculiar, the coxal 

 lines are not greatly turned outwards to form the coxal lobes, and at the same 

 time the separation between the two lobes is deep and elongate, so that the pro- 

 cesses have a greater extension in the longitudinal direction, and a less in the 

 transverse one than is usual, and the base of the articulation of the legs is more 

 imperfectly covered and protected ; in all the species (except Colymbetes nigriceps) 



