88 bulletin: museum of comparative zoology. 



first and second abdominal segments combined, very stout and blunt at the 

 apex. Wings hyaline, veins and stigma fuscous. Stigma long, narrowly 

 lanceolate, the radius originating beyond its middle; marginal cell moderately 

 long, acute at the tip, the second section of the radius twice as long as the 

 first. Submedian cell distinctly longer than the median. Areolet large, 

 regularly rhombic; discocubital and basal veins strongly arcuate. 



Type.— No. 2282, M. C. Z., Florissant, Col. (No. 6325, S. H. 

 Scudder Coll.). 



This species is more like recent ones than the foregoing ones on 

 account of the large rhombic areolet, the very typical abdomen and 

 ovipositor. It appears to be more like Mesochorus (Lithotorus) 

 cressoni Scudder from Green River, Wyoming, than any of the other 

 Florissant species. 



Mesochorus dormitorius, sp. nov. (Fig. 70.) 



Female. Length 6.5 mm. Black; prothorax, line before tegulae, tegulae 

 and legs including all coxae yellowish or reddish brown; the tibiae and tarsi 

 of the hind pair much darker. Abdomen below toward the apex brownish. 

 Antennae slender, with something over 30 joints, the ones near the apex but 

 little longer than thick; those near the base three or four times as long as 

 thick, the first flagellar still longer. Mesonotum finely shagreened; meta- 



thorax completely and distinctly areo- 

 lated. Abdominal petiole seen from the 

 side a little shorter than the posterior 

 face of the metathorax, weakly arcuate 

 and thickened apically from near the 

 base. Apical abdominal segments 

 strongly compressed, but this is prob- 



Mesochorus dormitorius, sp. abl ^ in P art due to flattening within the 



rock. Ovipositor at least as long as 

 the first two abdominal segments, and 

 probably longer as its apex is lost; its sheaths but slightly flattened. Wings 

 slightly infuscated. Stigma piceous; veins fuscous ; marginal cell about three 

 and one-half times as long as its greatest height; first section of the radius 

 slightly less than one-half as long as the second; areolet large, obliquely 

 rhomboidal, the first transverse cubitus two-fifths as long as the first section 

 of the radius. Stigma not especially broad, more lanceolate. 



Type.— Nos. 2283-2284, M. C. Z., Florissant, Col. (No. 13,778 

 and 13,826 (reverse), S. H. Scudder Coll.). The Scudder Collection 

 also contains a specimen, Fig. 70 (No. 11,970, M. C. Z., 2265) which 

 I refer to this species. 



