In order to clear up certain doubts which had arisen regarding the identity of several Heptagenine species, placed at present in the genus Ecdyonurus, and described by Clemens from material collected in the Go Home Bay region of the Georgian Bay (1913, Can. Ent. XLV, 246-262), Mr. G. S. Walley spent the months of June and July, 1932, in this same locality, collecting and breeding nymphal material. In the group in question he was most successful in securing both nymphs and bred adults of all the species listed by Clemens; the present article, therefore, is presented with a view not only of rendering definitely recognizable certain of Clemens' species in which the original diagnoses were rather brief and incomplete, but also of correcting some specific misidentifications occurring in Clemens' paper.