[In 1891 Mr. Chas. Robertson wrote (Tr. Am. Ent. Soc., XVIII., 49); “After careful study, I have been unable to determine more than two of Smith's species” of Andrena; and went on to explain that Smith's descriptions omitted certain characters which were necessary for the exact determination of the species. It is probable that Mr. Robertson did not have before him many of Smith's species, and hence, naturally, could not recognize them in his material; but it is nevertheless true that the determination of Smithian Andrenœ from the description alone is often a matter of great uncertainty.