During a recent study of the material in the family Phryganeidae in the Canadian National Collection, three nondescript species of the genus Prophryganea ganea Martynov have appeared. One of them, viz. P. deflata nov., is so close to P. improba (Hagen) as to be inseparable on any but the genitalic character illustrated herewith. As the range of P. deflata is very much that of P. improba (Hagen), it is questionable if the five ♂ co-types of the latter are conspecific; that one therefore which was deposited in the Canadian National Collection some years ago by Doctor Nathan Banks, is here designed lectotype, and its genitalia and alar nervation illustrated. This specimen and the genitalic slide are being returned for deposition in the Cambridge Museum of Comparative Zoology.