170 CHARLES ROBERTSON. 



Males. 



Pulvilli absent; segment 6 with two lateral spines, 7 with three terminal ones; 



ornaments pale yellow \ nl hid i mil. 



Pulvilli present; ornaments orange-yellow ; legs largely red- Diaiithidimii. 



STELIDINI. 



Females. 



Abdomen conical; segment 6 longer than 5, with carinate border; ventral seg- 

 ment 6 longer than 5, produced and curved downward, with a trans- 

 verse preapical carina; head with whitish ornaments; mandibles tri- 

 dentate; vein IV 2 before III 4 ; vein a opposite V 2 • • • Stelidimii. 



Abdomen depressed ; segment 6 not reflexed or carinate; head without whitish 

 ornaments; vein a opposite or a little before V 2 Microstelis. 



Males. 



Head with whitish marks ; abdomen conical Stelidi mil. 



H.:ul black ; abdomen ovate Microstelis. 



SPECIES. 



1. OSMUND. 



OSMIINI 

 Ceratosmia lignaria Say. 

 Centrosmia gn. nov. (Type Osmia bucephala Cressou), bucephala. 



OS MI A Panzer. 



Females. 



Scopa white, sometimes blackish on segments 5-6 ; clypeus entire ; joint 5 of max- 

 illary palpi minute pumila. 



Scopa black 1 . 



1. Head with pubescence pale 3. 



Head with pubescence more or less black ; mandibles 4-dentate 2. 



2. B r ight blue or purple; mesonotum with pubescence mixed with black. 



cobaltina. 

 Dull blue green; mesonotum with pubescence hardly mixed with black. 



brevis. 



3. Length 11 mm. ; mandibles 4-dentate major. 



Length 8 mm.; mandibles 3-dentate atriventris. 



Males. 



Segment 6 strongly notched ; dull greenish - -2. 



Segment 6 at most with a shallow notch 1. 



1. Bright golden green, abdomen more purplish- • • cobaltina. 



Brassy green ; margin of segment 6 testaceous pumila. 



2. Length 10 mm major. 



Length 8 mm atriventris. 



