carinated. Upper and lower figures.

The two varieties of A. virginea on this plate, are still more removed from the type of the species than those last figured; they are both much larger in size, and var. 4 presents a slight difference of formation, in having the basal volution somewhat carinated round the middle; but as in every other essential character it agrees with the rest, I have refrained from separating it as a distinct species.

The four varieties I have now illustrated of Ach. virginea, tend to establish, in a very complete manner, the correctness of the principles on which I have framed the specific characters of this genus; here are four shells, with a total difference in the colouring of each, yet all agreeing in the same formation. It should be observed likewise, that A. pallida, figured at pl. 41 of this work, and A. virginea, var. 4, are nearly the same in colour, while in formation they are completely at variance. I do not think it has been hitherto remarked, that the elegant green lines which ornament the common variety, are only external; they resemble, in this respect, the epidermis of other shells, for they may be taken off by a knife without any injury to the enamel. M. Ferrusac has figured several other varieties in his beautiful work on Land Shells.

Pl. 124

LICINIA Crisia.

Generic Character.—See Pl. 15.

Specific Character.

A. mas. Alis anticis falcato-acuminatis, fuscis, fasciâ mediâ margineque postico flavo; posticis infra flavescentibus colore griseo variis, basi maculis 4 fulvis.

Fem. Alis infra albentibus colore griseo variis; anticis integris, supra fuscis, fasciâ mediâ margineque postico albentibus; posticarum basi maculis 4 fulvis.

Male. Anterior wings angulated, brown, with a central band and hind margin yellow; posterior beneath yellowish marbled with grey, base with 4 fulvous spots.

Female. Anterior wings entire, above brown, with a central band and hind margin whitish; all the wings beneath whitish marbled with grey; base of the posterior with 4 fulvous spots.

Pieris Crisia. Godart. En. Méth. p. 197. Male. Drury, v. 3. pl. 37. f. 1. 2?

The extraordinary difference existing between the sexes of exotic Lepidoptera, and particularly among the Butterflies, (Papilionidæ Lin.) is a subject which hitherto has received but little attention; nor am I aware of any entomological writer who has described those characters which absolutely distinguish the sexes: characters which, I am persuaded, will hereafter be found of the first importance in a natural arrangement of these insects. But in the prosecution of this desirable object, the naturalist, as far as regards foreign Lepidoptera, will have to encounter serious obstacles; many individuals must be examined of each species, and some of these dissected. It falls to the lot of few to pursue their inquiries in the native regions of these insects. Collections in this country are very few, and some of these are not always open to the scientific labourer; neither can specimens be sacrificed for dissection, where there are not more than two or three individuals of a species.

This is in general a very rare insect; observed for the first time by Dr. Langsdorff and myself early in June (the tropical autumn), in a wood adjoining the Organ Mountains at Rio de Janeiro. From its local abundance, we were able to ascertain the sexes. The two upper figures are of the female, and the lower of the male insect.

Pl. 125

PAPILIO Nerius.

Generic Character.—See Pl. 92.

Specific Character.

P. (Gr. Ecaud.) Alis nigris, fasciâ communi maculisque viridibus; posticis dentatis breviter caudatis; his subtùs fasciâ subargenteâ, marginali, nervis divisâ. Godart.

P. (Gr. Ecaud.) Wings black, with spots and a common band of green; posterior wings dentated, obsoletely tailed, beneath with a silvery marginal band, divided by the nerves.

P. Nireus. Fab. Sys. Ent. 3. p. 36. Godart Ency. Méth. 9. 1. p. 48. Drury 2. pl. 4. fig. 1. 2. Cramer, p. 187. A. B. (mas.) pl. 378. F. G. (fem.)

I have figured this insect, principally because it will fully illustrate the first section (a.) in the arrangement of this beautiful family proposed at plate 92. The two divisions there adopted, after the manner of Linnæus, (Græci et Trojani) I am fully aware, are purely artificial; but the facility this distribution will give to the student, in searching after a particular species, is so obvious, that it need hardly be pointed out.

I have only had the opportunity of examining the individual from which the figure was taken. It is a male, having the anal valves rather lengthened and obtuse, with a small hook between them, which projects from the last segment of the abdomen. This circumstance proves the error of Cramer, in having mistaken the sexes of this species, both of which he seems to have figured. That which I apprehend is the female (Cramer, pl. 378, fig. F. G.) I have not myself seen. The blue-green on the upper surface of the wings is very resplendent and changeable, and the palpi and thorax beneath are covered with numerous whitish spots.

On the under side of the inferior wings, near their base, is a paler band, rayed with the nerves, and in some lights shining with a pale silvery reflection.

Mr. Smeathman sent this species from Sierra Leone, in Africa, to Mr. Drury. The locality, therefore, of India, given by Linnæus and Fabricius, must be incorrect.

Pl. 126