The Pselaphid.« of North America. 39 



of amcn'caniDii, differing chiefly in the base of the head, which 

 is not channelled or at most scarcely visibly impressed; the 

 prothorax is at least as long as wide, much longer than in 

 amei'icanum^ with conspicuous lateral foveas. Elytra about 

 the same as in ^w^cr/ifrtw/^w, seemingly not so convex from side 

 to side. Length 0.5 mm. 

 Habitat. Southern States. 



AcTiuM, Casey. 



Body more robust than in Trimmvi, head smaller in pro- 

 portion, the shoulders broader. The palpi are short, the last 

 joint ovate, acuminate, thick. The elytra have three basal 

 punctures and long, well impressed, discal lines; there is a sub- 

 humeral fovea in connection with a deeply impressed line on 

 the declivous lateral part of the elytra, parallel to the marginal 

 impressed line. The marginal line is also a constant mark 

 in Trimiuni. 



A. PALLIDUM, Casey. Slender, convex, yellow; pubescence 

 very fine, recumbent, not conspicuous; body polished, impunc- 

 tate. Length 1.2 mm. Plate XI, Fig. 99. 



Head small, much narrower than the prothorax, as long as 

 wide, eyes finely facetted, prominent, large; tempora shorter 

 than the eye, not prominent, occiput impressed in the middle; 

 there are two pubescent foveae in the eye line, mutually twice 

 as distant as either from the eye, connected by a wide, broadly 

 arcuate channel. Antennce short, one-half longer than the 

 head, first and second joints subequal, larger; third to seventh 

 subequal, becoming gradually shorter and more transverse; 

 eighth to tenth transverse, equal in length, gradually wider; 

 tenth three times as wide as long; eleventh wider, as long as 

 the five preceding together, ovoid. Prothorax nearly as wide 

 as long at one-third of its length from the neck, where the 

 sides are evenly rounded and nearly straight to the basal 

 angle; the base is arcuate and thinly margined; disk very 

 convex, transverse sulcus deep, one-fourth from the base, 

 angulated towards the base in the middle, connecting the large 



