30 COLEOPTERA OF NORTH AMERICA. 



As above constituted the tribe contains in our fauna two 

 groups, separated in the following manner: — 



Terminal joint of palpi more or less cylindrical and obtuse at tip, that of 

 the labial as long as the j) receding. Pogoni. 



Terminal joint of palpi slender, acute at tip, that of the labial palpi 

 shorter than the preceding. Trechi. 



J.n addition to the above characters the form of the paraglossse 

 and the setoe of the ligula add some weight to the separation of 

 the two groups. 



Group I. — Pogoni. 



This group contains in our fauna two genera : — 



Head more or less constricted behind the eyes or transversely impressed ; 

 elytra not margined at base. Patrobus. 



Head not constricted behind the eyes ; elytra usually margined at base. 



Pogonus- 



These two genera are represented on both sides of the con- 

 tinent. 



Group II. — Trechi. 



This group contains in our fauna two genera which have the 

 second joint of the antennse somewhat pubescent ; they are as 

 follows : — 



Head with distinct eyes ; anterior tibire slightly broader to tip, the emar- 

 gination extending nearly to the middle of the tibia. Trechus. 



Head without eyes ; anterior tibiae slender, the emargination at apical 

 third. Anophthalmus. 



Our species of the latter genus may be divided in two series; 

 the first contains Tellkampjii, in which the last joint of the 

 maxillary palpus is very distinctly shorter than the penultimate ; 

 the second comprises all our other species with the same joint 

 equal to, or even a little longer than, the preceding. 



The suture between the mentnm and its support is often 

 entirely obliterated, especially in Anophthalmus, and is very 

 indistinct in some Patrobus, although sufficiently marked in 

 others, and in nearly all Trechus. 



Tribe XVIII.— PTEROSTICHIXI. 



Antennae arising under a distinct frontal ridge, the three basal 

 joints glabrous. Head more or less constricted behind the eyes, 



