•1S64.] 29 



abdomen blue ; the antennae a little longer than the head and thorax, 

 setaceous, fulvo-testaceous beneath ; the face thickly covered with long 

 white pubescence, a similar pubescence is also more thinly scattered 

 over the vertex, thorax and base of the abdomen ; wings as in the 

 female ; the apical segment notched in the middle ; beneath, the ven- 

 tral se"-meut is bidentate." 



Hah. — Nova Scotia ; United States (Smith) ; Connecticut ; Great 

 Slave Lake, British America. Two $ specimens. Coll. Mr. E. Norton. 



I have not seen the male of this species, and am somewhat uncer- 

 tain that the female specimens from which I drew up the above de- 

 scription are the true similUma of Smith, as his description does not 

 quite accord with the specimens 1 have examined. 



18. 0. atriventris, u. sji. 



Fvinale. — Head subquadrate, as wide as the thorax, dull blue-green, 

 strongly tinged with blue about the clypeus, densely and somewhat 

 finely punctured, clothed above and beneath with rather long white 

 pubescence ; anterior margin of the clypeus slightly and obtusely emar- 

 ginate ; mandibles black ; antennae rather longer than the head, black, 

 the scape slightly tinged with green and the flagellum beneath with 

 rufo-testaceous. Thorax dull blue-green, densely and finely punctured, 

 clothed above and beneath with rather long white pubescence ; disk 

 in front with a finely impressed longitudinal line, and on each side 

 above the teguljB a small smooth shining spot ; tegulae black, shining. 

 Wings subhyaline, faintly clouded ; nervures black. Legs black, shin- 

 ing, thinly clothed with short pale hairs. Abdomen short, subglobose, 

 dull blue-green, shining, densely and finely punctured, clothed with 

 whitish pubescence, which is long on the basal segment, shorter on the 

 sides and apex of the abdomen and very short on the segments above ; 

 beneath, the ventral scopa is dense and black. Length 4 lines. 



Ilab. — Connecticut. Two specimens. Coll. Mr. E. Norton. 



Resembles similUma, Smith, but is much smaller and the punc- 

 tation of the abdomen much more dense and rather finer. 



Ut. 0. dubia, n. sp. 



Frmalc. — Head large, subquadrate. rather wider than the thorax, 

 dark blue-green, clypeus deep blue, finely and den.sely punctured, 

 rather thinly clothed with whitish pubescence which is slightly inter- 



