NORTH AMERICAN COLEOPTERA. 165 



ON THE PSEL,AI>IIID GEXUS TRIMIl.M. 



BY EMIL BRENDEL, M. D. 



The classification of the species of this genus is perhaps the most 

 difficult of all tiie Pselaphidie; not only on account of their small 

 size, but by their less salient marks of distinction. Most of the de- 

 scriptions of our species, so far known, are but a continual repetition 

 of the properties common to all of them and optical delusions in 

 measuring the dimensions of the parts have led to errors. The com- 

 mon characters of this genus are as follows : 



Posterior coxse contiguous. Abdomen narrowly bordered, circularly convex, 

 dorsal segments subequal, or the first visible doi-sal somewhat longer, the fourth 

 never longer, the second ventral (or the first visible one) longer than any one 

 of the succeeding ones. Antenuis short, not much longer than the head, second 

 joint larger than the first, the intermediate of equal length, ninth and tenth 

 transverse, but never as wide as tlie base of the last joint, the latter being of a 

 thick ovate form as long, or longer than half of the intermediate joints together. 

 Head with two fovete and a circumambient sulcus. Pronotum very convex, 

 with an autebasal transverse sulcus. Elytra each with a sutural line and two 

 basal fovese prolonged backwards. 



The characters for the distinction of the species known to me are 

 as follows : 



Eyes nearly in a level with the vertex foveicolle. 



Eyes far down on the sides of the head. 

 Head narrower than the prothorax. 

 Pronotum impunctate. 

 Sulcus on the vertex interrupted in front. 



Prothoi'ax wider than long, base of dorsum with two short carinre. 



Length 1.4 mm iiiipiiiictaliiin. 



Prothorax as wide as long (seemingly longer), dorsal base not carinate. 



Length 1.2 mm diiruiii n. sj). 



Sulcus of the vertex entirely circumambient. 



Shoulders prominent, their width as wide as the prothorax. 



.Antenme not longer than the head, last joint very large, prothorax 

 wider than long, base of dorsum with two short carinre. Length 



1-5 mm globiler. 



Antennse longer than the head, prothorax as wide as long. 



A})dominal cariniB divergent, two-thirds of the length of the seg- 

 ment, occiput only on the basal declivity sulcate. elytra very 



convex. Length 1.2 mm coiiifalo ti. sp. 



Abdominal carinre not visible. Length 1.05 mm ((raoilt* n. sp. 



Shoulders not prominent, narrower than the prothorax. Length O.ii mm. 



auiericaiiiiiii. 



TRANS. AM. ENT. SOC. XIX. JUNE, 1892. 



