I wish to draw particular attention to this genus and its allies. I have, in 1865, drawn a parallel between the group and the Hawk Moths, from the young stages and the peculiar pupation, and in my pamphlet on “the Hawk Moths of North America,” I hae discussed the probabilities of their relationship. But I here wish to point out that the group is American; that in America we may except to find old types among that portion of the fauna which is indigenous, pre-tertiary, and to this Citrheronia belongs.