536 PROCEEDINGS OF THE ACADEMY OF [1893. 



femora, except apex, black; legs feebly spiuose. Length 5? mm. 

 Colorado; Nevada. Seems to be very rare. 



PLENOCULUS Fox. 

 Plenoculus Fox, Psyche, Nov. 1893, p. 554. 



Outer margin of mandibles strongly emarginate; in the $ the clypeus 

 has on each side a fringe of hairs as in Cerceris; eyes within not emar- 

 ginate, distinctly converging towards the vertex; ocelli round and 

 prominent, all three distinct, placed in the form of a triangle ; anten- 

 nae short and stout, originating immediately behind the clypeus, the 

 flagellummore or less clavate; head transverse, wider than the thorax; 

 pronotum not reaching the level of the dorsulum; metatkorax 

 shorter than the dorsulum ; legs stout, the femora narrower at apex 

 than at the base, tihiai and tarsi strongly spinose, anterior tarsi with a 

 tolerably well- developed comb ; tibial spurs large, the hind tibia? with 

 two, the four anteriors with but one; tarsal claws rather long and 

 slender, entire, smaller in the S ; wings with an elongate marginal 

 cell, which is truncate at apex and with a small though distinct ap- 

 pendiculation, three submarginals of which the first is nearly twice 

 as long as the other two combined, the second petiolate, the third is 

 oblique and slightly narrowed above, first recurrent nervure re- 

 ceived by the first submarginal cell near its apex, the second by the 

 second submarginal cell between its middle and apex, the discoidal 

 and basal nervures meet at a short distance from the apex of the 

 submedian cell, this cell being therefore shorter than the median cell on 

 the externo-medial nervure, stigma small, scarcely distinguishable 

 from the costal nervure; last dorsal segment of 9 with a large and 

 distinct pygidial area. 



Three species of this genus are known at present, all of which 

 occur in the United States. 



Clypeus strongly emarginate medially and dentate laterally; first 

 joint of flagellum, if anything, shorter than the second. 

 On each side of the clypeal emargination there are from three to 

 five small teeth; mandibles, except apex, and hind tibia? and 

 tarsi (usually) more or less, yellowish; $ with the clypeus, 



teguhe, tibia' and tarsi, yellow; abdomen black Davisii. 



On each side of the clypeal emargination, though widely sepa- 

 rated from it, are two large and prominent teeth; mandibles red- 

 dish medially; hind tibia? and tarsi not at all yellowish; $ un- 

 known; abdomen black propinqum. 



