As far as the neuration is concerned (excepting that of the costal nervure, which is certainly incorrectly rendered, and does not accord with the description) it agrees sufficiently with the general neuration of Mylothris[AB] to suppose it may belong to the allied genus Mylothrites, but that it can belong to _M. Pluto_ is exceedingly improbable, as one may judge by tracing the probable extent of the broken hind wing, and placing the tracing in juxtaposition with the fore wing of Pluto, as in the accompanying woodcut (fig. 1); for it must be remembered that in all the genera of this subfamily, the cell extends at least to the middle of the wing; the hind wing of _M. Pluto_ must, therefore, have certainly been fully one-sixth longer than the wing conjectured to belong to it; so great a difference is at least unusual among individuals of the same species in this group; moreover, the neuration is not quite what we should expect, although the appearance of veins on the drawing we have reproduced must be in part due to extraneous causes; we will, therefore, make no attempt to decipher the present condition of the fossil, trusting that some of the Austrian lepidopterists will give the subject early attention. A study of the original description and illustration of the front wing of this butterfly leads me to the conclusion that the description of the neuration of the fossil was drawn up from the illustration and not from the fossil itself. Both agree in the points in which my drawing (Pl. II, fig. 7) differs from them; and since in these very points they will not harmonize with the neuration of any living Lepidoptera, while the drawing I present agrees as well as could be desired with certain of them, I am forced to believe the original drawing published by Heer, and the accompanying description, presumably founded upon it, to be incorrect. I am acquainted with but very few living butterflies[AC] in which a nervule is emitted from the inferior side of the subcostal nervure nearer the base of the wing than any of the superior nervules of the same vein; this is the manner in which the neuration of this butterfly is represented in Heer’s plate and in his description, if read carefully in connection with the plate; although he does not tell us on which side of his _zweite Hauptast his dritte Hauptast_ originates. The description given by Heer of the markings of the fore wing is more complete than I have been able to offer from an inspection of drawings alone; it differs, too, in one somewhat important point, in that what I have called a broad lighter belt with blackish dots in each interspace, he has described as a series of pale circular spots as broad as the interspaces, each containing a blackish pupil. A reëxamination of the fossil upon this point is desirable; the only indication of such circular pale spots in my drawing is the curved boundary in each interspace between the darker and lighter portions.