418 COLEOPTERA OF NORTH AMERICA. 



Sub-Tribe 2.— IVeiKiognatllilli. 



Head triangular, squarely truncate behind (except in Gna- 

 thium) ; front with distinct transverse suture, prolonged beyond 

 the insertion of the antennae, which are filiform or very slightly 

 thickened externally; the eyes are transverse, rarely (Gnathium) 

 oval and oblique ; the mandibles are acute at tip and extend 

 beyond the labrum; the outer lobe of the maxilla3 is generally 

 prolonged into a slender, flexible process, sometimes nearly as 

 long as the body; the maxillary palpi are not dilated, and the 

 last joint is longer than the preceding; the claws of the tarsi are 

 cleft to the base, the upperportion is strongly pectinate, the lower 

 one equal in length, acute, and generally more slender than the 

 upper; the tarsi are clothed with stiff hairs beneath. 



The serratui-e of the upper part of the claws is not sufficient 

 by itself to separate this from the fifth sub-tribe, since in it there 

 are certain foreign genera, scarcely to be distinguished in appear- 

 ance from Cantharis, in which the upper part of the claws is quite 

 distinctly serrate; but the marked difference in appearance pro- 

 duced by the triangular head, which is usually applied more closely 

 than in Cantharis to the square prothorax, and especially the more 

 prominent and acute mandibles, evince the propriety of separating 

 the three genera below mentioned from those contained in that 

 sub-tribe. 



Maxillse with the outer lobe prolonged, isetaceous ; 



Antennae not thickened externally. Nemognatha. 



Antennae thicker towards the tip. Gnathium. 



Maxillse with the outer lobe not prolonged. Zonitis. 



The species of Nemognatha differ like those of Cantharis in the 

 size and shape of the spurs of the hind tibite; in Gnathium, the 

 prothorax, instead of being square, as in the other two genera, is 

 gradually narrowed in front, but, as if to balance this approach 

 towards the next sub-tribe, the mandibles are still longer and 

 more acute than in Nemognatha. 



Sub-Tribe 3.— Sitarini. 



Head triangular, suddenly constricted behind; front with dis- 

 tinct transverse suture, prolonged beyond the insertion of the 

 antennae, which are rather stout, not thickened externally. The 



