Fossorial Hymenoptera of North America. 393 



lum more equal than iu Passalxciis, where there is a greater dispropor- 

 tion, being much shorter and transversely linear. The form of the 

 propodeum is intermediate between that of Cemonvs and Passal&cus, 

 being much shorter than in the latter, and very rugose, with no dis- 

 tinct enclosure at the base, and with no well marked mesial furrow. 

 Tbe structure of the wings allies it closely to Passalsecus ; the stigma 

 is very distinct; the third costal (or radial) cell is less triangular than in 

 the succeeding genus, but much more so than iu Cemonus ; 2d subcos- 

 tal (cubital) cell is very short, one-half as long as wide, subtrapezoidal; 

 2d median cell distinctly rhomboidal, where in Cemonus the inner side 

 (or 1st recurrent) is curved, and not parallel to the outer oblique 

 side, (or 2d recurrent), being much as in Passaltecus ; 3d median cell 

 shorter and broader than in Passalsecus, since the outer side is longer 

 and more sinuate. 



Abdomen a little longer than the thorax, where in the succeeding 

 genus the two are very nearly equal in length ; subsessile, thickest near 

 the base ; short ovate, rings not so contracted at the sutures as in the 

 two other genera, being full and very convex above; tip acute, with a 

 rather broad flattened well marked, triangular area. 



This genus may be readily known by the triangular supraiinal flat- 

 tened area, which is large and conspicuous; by the striated clypeus 

 and exserted bidentate labrum, from which the generic name is de- 

 rived. The want of the usual pubescence on the front of the head, 

 the very long slender mandibles, not increasing in width as in Passa- 

 laccus, where the head is shorter in front than in that genus, will dis- 

 tinguish it. 



But a single species has yet been detected in this country. 



D. americanus, n. sp. 



9 . Body black, shining and polished, clypeus smooth and shining; 

 antennae entirely black; scape black; mandibles white, reddish at the 

 tip ; palpi dark fuscous; surface of the head smooth, polished, with 

 much fewer minute shallow punctures than usual, scarcely pubescent, 

 except on the orbits, where it is thinly so. Meso-scutellum, with the 

 mesial and sub-mesial lines distinct, parallel, very contiguous, surface 

 anteriorly more densely and minutely punctured than on the disk; 

 meta-scutellum more fully colored than scutellum ; propodeum with no 

 distinct enclosure, or distinct mesial furrow; anterior portion with no 

 unequal parallel straight lines proceeding from the base ; posteriorly 

 an irregular net-work of shallow broad fossulets. Tegulae and inser- 

 tion of the wings testaceous ; nervures blackish, pterostigma black ; 



PROCEEDINGS ENT. SOC. PHILAD. FEBRUARY, 1867. 



