362 iNli. T. D. A. Cockcrcll — Desert) ilions and 



twice as far from its base as secoiul from its apex. Abdomen 

 parallel-sided, first segment with white hair (some black at 

 extreme sides) ; second with thin white hair and shorter 

 black hairs intermixed, especially at sides, but inconspicuous ; 

 remaining segments with black hair, but third with a little 

 silvery white on margin laterally ; sixth segment with a 

 broad shallow notch, seventh bidentate ; second and third 

 ventral segments shallowly emarginate, with a very little 

 shining reddisli hair in the emargination. 



Very close to 0. marginipennis, Cresson, but distinguished 

 by the strongly green mesothorax and scutcUum, the paler 

 liair of thorax above, the edge of clypeus not " subsinuate," 

 and the apical margin of wings not so dark. It also much 

 resembles 0. cyaneoniteiis, CklL, but differs thus: — 



Smaller : hair of pleura all -white ; middle tibia with con- 

 spicuous white hair cyaneonitens. 



Larger : hair of pleura partly black ; middle tibia with 



black hair viridior. 



Hah. Boulder, Colorado, May 20, 1906 (-S'. A, Rohwer). 



Osmia olivacea, sp. n. 



^. — Length about or nearly 10 mm.; anterior wing 7-|-; 

 width of abdomen 3|^. 



Olive-green, the sides of the thorax dark blue-green ; hair 

 of head and thorax long and abundant, white on cly])eus, 

 cheeks below, and lower part of pleura, but otherwise tawny, 

 with very long black hairs intermixed on thorax above, 

 vertex, cheeks, and a few at sides of face; head normal, 

 lower edge of clypeus straight, the bidentate mandibles with 

 their teeth strongly divergent ; hair of upper part of face 

 strongly tawny; antennae long, black; flagellum slightly 

 moniliform or crenulate; vertex and mesothorax rough with 

 exceedingly dense punctures; a little shining space bordering 

 anterior ocellus in front. Legs black, the iiind coxae and 

 femora dark green, and a slight green tint on middle ones ; 

 anterior and middle femora wath long pale hair behind, hind 

 femora with dusky hair ; hair of tibiae (excej)t anterior ones 

 behini;) daik ; hair on inner side of hind tarsi golden ; spurs 

 normal; tegulae green. Wings dusky, hyaline before the 

 broad apical area; first r. n. joining second s.m. about 1^ 

 limes as far from its base as second from its apex. Abdomen 

 shining olive-green, the hind margins of segments con- 

 colorous; first two segments with pale hair, the others with 

 black hair, quite long, and a little pale intermixed; sixth 



