Nomada obscurella Fowler, 1902, was originally described from one male from Berkeley, California, March 18, from Ranunculus californicus, under the name N. obscura Fowler, 1899 (preoccupied). Nomada fowleri Cockerell, 1903, was described from a female from Corvallis, Oregon, April 15, 1897 (A. B. Cordley). In connection with a study of some interrelationships of some Ranunculus bees we have become convinced that the two are synonymous. Although in general we disapprove of the association of sexes by elimination, in this case we regard the circumstantial evidence so strong as to leave little doubt that they represent the two sexes of a strikingly sexually dimorphic species.