526 COLEOPTERA OF NORTH AMERICA. 



base truncate, witli a transverse elevated line, whicli is either 

 antebasal (Tropiderini) or entirely basal ; this line is abruptly 

 bent forwards at the sides, and forms a more or less abbre- 

 viated side mai'gin. 



The prosternal sutures are entirely obliterated, as is also 

 the short suture behind the posterior point of the pro- 

 sternum, so that the under surface consists of but one piece. 

 The coxal cavities are rounded and narrowly separated. 



Mesosternum flat, triangular behind, with the point 

 rounded, and separating the middle coxje; cavities rounded, 

 epimera transverse, oblique, not attaining the coxse. 



Metasternum long, side pieces narrow, or moderate in 

 Avidth, wider in front, with the outer angle prolonged for- 

 wards; in many genera there is a transverse impression in 

 front, simulating a suture. 



Elytra conjointly rounded behind, and forming a small 

 sutural fold, which fits into a deep emargination of the 

 pygidiura; fold of the inner surface acute, not prolonged 

 much behind the middle. Epipleurse distinct. The striee. 

 are ten in number, with a short scutellar one as in Carabidae; 

 this scutellar stria is usually about one-fourth the length of 

 the elytra, and does not connect itself with the sutural stria. 



Abdomen with five free, and sometimes nearly equal 

 ventral segments; sutures straight; intercoxal process tri- 

 angular, acute, or rounded in front ; dorsal segment mem- 

 branous, except the pygidium, which is corneous, declivous, 

 and exposed; no anal segment in the %. 



Anterior cox« narrowly separated, globose ; middle coxae 

 moderately separated, rounded; hind coxas transverse, not 

 prominent, never very widely separated. 



Legs slender, front pair sometimes elongated in % ; tibiae 

 truncate at tip, without spurs or hooks. 



Tarsi brush-like beneath, i-jointed; second joint triangu- 

 lar, cmarginate; third joint bilobed, sometimes large, some- 

 times small ; fourth joint slender with divergent claws, which 

 are either simple or toothed. 



Our g;enera represent four tribes: — 



Antennae inserted at the sides of the beak ; 



Protlioracic ridge not basal. Tkopidekini. 



Prothoracic ridge basal. Basitkopim. 

 Antennae inserted on the front : protlioracic ridge basal; 



Elytra striate as usual. Ar^ocerini. 



Elytra not striate. Xenorchestini. 



