[41] NORTH AMERICAN COLEOPTERA. 197 



are not spongiose, and not connected by the anterior arcu- 

 ate groove, the latter terminating posteriorly in two very 

 deep foveas just in advance of the occipital pair. Elytra 

 each with with three foveas at base, the lateral prolonged 

 posteriority in two divergent striae. 



The structure of the abdomen differs decidedly in the two 

 genera, although Trogaster has the short basal segment, the 

 second ventral is but very little longer than the third. In 

 Trogaster the first three visible dorsal segments are nearly 

 equal; in Oropus these decrease uniformly and rapidly in 

 length. Amauronyx agrees well with the present genus in 

 abdominal structure, but has the posterior coxae separated 

 as in Trichonyx, the elytra with but two basal fove.e, and 

 the pronotum without lateral teeth. 



I have drawn my comparisons from specimens of Amau- 

 ronyx Maerkeli Aub.; Trichonyx sulcicollis Reichb., and Tro- 

 gaster aberrans Sharp, very kindly given me, together with 

 many other Pselaphides and Scydmasnides, b}^ Capt. Ch. 

 Kerremans of the Belgian army. 



Oropus has thus far occurred only on the Pacific Coast; 

 one species has already been described by Dr. Le Conte 

 under the name of Trichonyx striatus; I now add three others 

 from more southern latitudes, of which convexus is assumed 

 to be the type of the genus. 



In the following descriptions the elytra! stria? are desig- 

 nated by the numbers one to four, in order from the suture 

 outward. 



The four species may be distinguished as follows: — 



Elytral stripe two and three subequal, extending distinctly behind the 

 middle. 

 Pronotal cmaliculation not intenupted before the transverse basal 

 groove. 



Canalicnla'ion dilated anteriorly Striatus. 



Caual.culation not dilated anteriorly, coarse, dilated in the middle, 



convexus. 



Canalicnlation completely interrupted behind the middle. . . interrupts. 

 Elytral stria' two and three unequal, snorter abbreviatus. 



