I think I have satisfactorily identified this species. I captured a specimen at Yosemite, California, on June 5th, 1891, that bears out Boisduval's description. The specimen, however, is Cerura aquilonaris, Lintn., and these names will have to be considered as referring to the same species. I have also received a specimen from Mr. C. A. Wiley, of Miles City, Montana, so the species probably occurs from the Atlantic to the Pacific.