Fig. 1. The dotted outer border of the hind wing represents the probable limit of the Gratz fossil. The broken outer border indicates the probable size of the hind wing of Mylothrites Pluto.
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.
Tertiaries of Radoboj, Croatia. Fore wing, Hof-Mineralien Kabinet, Vienna. Hind wing, Museum of Gratz, Austria.
COLIATES Scudder.
The fore wing ([Pl. II], fig. 5) is slightly more than twice as long as broad; the costal border is straight for fully two-thirds its length, and then curves gradually and slightly downward, the apex rounded off; the outer margin has a nearly regular and slight convexity, but is nearly straight in the middle half; the lower outer angle is rounded and the inner margin slightly convex. The costal nervure scarcely reaches the middle of the costal border; the discoidal cell is but little more than half the length of the wing; the subcostal nervure has but two superior branches, although the outer is not only itself forked, but its upper fork is branched at the extreme tip of the wing; the first superior nervule is emitted at some distance previous to the tip of the cell, or opposite the base of the first median nervure; it terminates in the middle of the outer half, of the costal margin, and the forked branch of the outer superior nervule supports the extreme apex of the wing; the inferior subcostal nervule arises midway between the bases of the two superior nervules, and terminates about one-third way down the outer border; the vein closing the cell strikes it near the base and has an inward convexity, meeting the upper median nervule farther from its origin; the first median nervule originates at some distance beyond the middle of the cell.
In the form of the wing and its neuration this fossil group is more nearly allied to Delias ([Pl. II], fig. 4) than to any other genus I have been able to examine. It is plain at first glance that it must be placed in the vicinity of Delias, Thyca, Prioneris and similar East Indian Fugacia, in which there are but two superior subcostal nervules, and in which the outer of these is forked; but I have met with no instance among these in which one of these forks is itself branched; and this insect differs notably from them all in the elongate form of the wing, the remarkably straight costa[AD] and the shorter discoidal cell; and from all Pierids in the shortness of its costal nervure and the basal extension of the first superior subcostal nervule; this latter nervure always originates, in every living type I have examined, at or beyond a point opposite the middle of the space between the bases of the first and second median nervules.
COLIATES PROSERPINA Scudder.
[Plate II], fig. 5.