1« [April 



small shining tubercle ; mandibles very stout, rugose and clothed with 

 short fuscous pubescence, their apex broad, armed with three short 

 teeth, the innermost one blunt, and the two outer ones approximate 

 and subacute; lower margin of each mandible with a deep longitudinal 

 channel, and a large irregular tubercle at the base immediately below 

 each extreme lateral angle of the cljpeus ; inner orbits of the eyes 

 acutely carinated ; antennae about the length of the head, black. Tho- 

 rax black, finely and very closely punctured; densely clothed with 

 rather long pubescence which is ochraceous above and on the sides, 

 and fuscous beneath ; tegulas black, .shining and feebly punctured. 

 Wings fusco-hyaline. apical margin paler ; nervures blackish. Legs 

 black, clothed with black or fuscous pubescence. Abdomen subglo- 

 bose, black with a greenish-blue reflection, minutely punctured, pol- 

 ished ; basal segment above thickly clothed with rather long ochrace- 

 ous pubescence ; the second segment with dark fuscous pubescence 

 intermixed with ochraceous on the anterior part ; third, fourth and 

 fifth segments with short black pubescence ; apical segment clothed 

 with very short ochraceous pubescence ; beneath the ventral scopa is 

 dense and black. Length 7h lines. 



Hab. — Gi-reat Slave Lake, British America. One specimen. Coll. 

 Smithsonian Institution. 



This and the next species are at once distinguished from all others 

 known to me, by the large size, robust form and the unusually large 

 head. Both species closely resemble each other, but are sufficiently 

 distinct by the characters given in the descriptions. 



2. 0. megacephala. n. sp. 



Female— Head very broad, subquadrate, rather larger than the 

 thorax, black with a slight bluish reflection, densely and somewhat 

 strongly punctured, clothed with rather long black pubescence, except 

 a tuft above the insertion of each antenna which is ochraceous, the 

 pubescence dense on the face and clypeus and sparse on the vertex ; 

 clypeus and mandibles as in the preceding species ; inner orbits of the 

 eyes acutely carinated ; antenufe about the length of the head, black. 

 Thorax closely and somewhat strongl}^ punctured, black, densely clothed 

 with rather long ochraceous pubescence, with a slight mixture of black 

 on the disk above ; metathorax opaque blue-black, very minutely punc- 

 tured, with a deep impression on its disk ; tegulte black, shining, feebly 



