The Pselaphid^ of North America. 225 



Vertex not foveate prothorax faintly trifoveate, under surface of 

 head bicarinate body broad, antennal club three-jointed, only 

 four ventral abdominal segments visible. - Nisaxis, Casey. 



Vertex and pronotum trifoveate, body broad, each elytron with a 

 long discal line, antenna; with a three-jointed club, under sur- 

 face of head unicarinate. - - - Bryaxis, Leach. 



Vertex bifoveate with a transverse frontal impression and abso- 

 lutely circumambient sulcus, prothorax trifoveate, only the 

 last antennal joint enlarged, body elongate. E upsexi us, Z,ec. 



b* Body convex abdominal border narrow, prothorax without, or with one 

 basal fovea, base of the abdominal dorsum without carince, or only 

 indications of them, mutually far distant. 



Pronotum not foveate, elytral lines wanting vertex impressed in 



front. PsELAPTUS, Lee. 



Pronotum unifoveate, elytral lines present, the discal ones very 

 short, vertex and antenn:e differently sculptured in the sexes. 



Verticixqtus, Brcndel. 

 Vertex with four faint fovere different in the sexes; prothorax 

 bifoveate, with a shallow basal transverse sulcus; elytral 

 discal lines obsolete or wanting, sutural lines present, abdom- 

 inal border on each segment not triangular, basal carinae 

 present. Sexual differences in the vertex, antennae and an- 

 terior tibia;, tarsi with two unequal claws. Arth.mius, Lee. 



b^ Body circulo-cylindrical, narrow, elongate, very convex; abdominal mar- 

 gin w iih the edges not parallel, triangular on each segment, the ex- 

 ternal edges obsolete; vertex arcuately impressed. Prothorax with 

 two or three longitudinal grooves, claws two, unequal. Batrisl's, Lee. 



a- Posterior coxie approximate. 



d^ Body circulo-cylindrical, narrow, vertex arcuately impressed, prothorax 

 without longitudinal sulcus, the last antennal joint only enlarged, 

 tarsi with a single claw (Trimiiui). 



Elytral base bifoveate, no subhumeral fovea, head larger. 



Trimium, Aubi, 

 Elytral base trifoveate, with a subhumeral fovea, head smaller. 



AcTiUM, Casey, 

 d* Body elliptico-cylindrical, convex, broader, the last three antennal joints 

 enlarged, head transverse, prothorax with sharp, straight, linear longi- 

 tudinal and basal sulci crossing each other, tarsi with two unequal 

 claws ( Trogasterini.) 



e^ Prothorax at sides not spinous. Elytra with four basal punctures, each 

 with a line, the discal ones abbreviated. - - Rhexidiis, Casey. 

 e^ Prothorax at the sides spinous. 



Prothorax armed at the sides with a single sharp tooth, elytra 

 with three discal lines. ... - Oropus, Casey. 



