in the same state. If some of the drawers containing the species of Succinea were to be overturned, the shells would have to be redescribed, for neither the authors of the species, nor any other conchologist, could ever rearrange them in the same order again. It would be well if the spectacles of the learned author of Cyclade could be placed with the species, for it is quite certain that without them no other conchologist will ever be able to recognise them. The Ampullariæ are in such an unsatisfactory state of arrangement, notwithstanding the generic sub-divisions, that the locality is of much more importance to the student than either the form or marking of the shell. The Melania are in such a hopeless state of confusion that the species are only to be discovered by means of some supernatural agency; and the genus Conus has numerous genera within itself, a circumstance so remarkable, that it is impossible to say how such a curious phenomenon could have been brought about. Formerly, capital characters were obtained from the shells, so as to leave no doubt about the best mode of distinguishing them; but varieties, confound 'em, have crept in and spoiled all. The poor animals have been cut to pieces in every direction, to try and find something there, but the success has been about equal to the early trials; it has resulted in a complete failure; every supposed permanent character has turned out to be so variable that it cannot be trusted. Species-making was a good paying business, particularly to the men out exploring, and now genera-making is the order of the day, to suit the altered times. A beautiful variety was not to be thought of; it must be a distinct species, and the silly fellow who possesses it must boast of having the only one, no matter at what price.

By far the greater number of shells to which the term species has been erroneously employed, are simply intermediate varieties of variable species. Mr. Reeve makes a

very curious admission with regard to what he considers intermediate species; he says, "if we were to consider that because a species occurs between two others, it is a certain indication that the three constitute but a single species." If we admit this, a large number of our named species would become varieties. There are innumerable shells of every grade of variation, not only in the middle, but filling up every stage, and connecting at least half-a-dozen of the shells now bearing the title of species into one group, or, if the term is preferred, into one species.

The N. costata, A. Ad.; N. labida, Reeve; N. micans, A. Ad.; N. multicostata, A. Ad.; N. cuvierii, Payr.; N. incrassata, Mull.; N. nodifera, Powis ; N. crenulata, Reeve (Brug?); N. cremata, Hinds; N. reticosa, A. Ad.; N. gemmulata, Lam. ; N. cumingii, A. Ad.; N. verrucosa, A. Ad., not Gmel; N. candens, Hinds; N. stigmaria, A. Ad.; N. marginulata, Lam.; N. crenellifera, A. Ad.; N. sequijorensis. A. Ad.; N. plicatella, A. Ad.; N. reticulata, Linn.; N. margaretifera, Dunk.; N. ravida, A. Ad.; N. variegata, A. Ad.; N. festiva, Powis ; N. tritoniformis, Kien; N. acinosa, Gould; N. nivea, A. Ad.; and N. dentifera, Powis; all belong to one and the same series, and are all intermediate varieties.

So far as my knowledge extends, not a particle of information on the subject of the external variation of sculpture is to be found in the works on conchology, either ancient or modern. If any number of men were to commence the study of a special branch of conchology at the same time (and they may be all equally eminent), at the end of their work it would be found that no two of them were alike in their conclusions; and if they were to write upon the same genus, each devoting a similar amount of time to the subject, the resources of each would be different; or if they all worked from the same collection

of objects, their opinions would differ with regard to some of them. One would examine his specimens critically, and take in every slight shade of difference that they might present; another would be satisfied with their general resemblances to the published figures, and make allowances for the slight variations; while a third, with a less critical eye, would be certain to commit errors, in fancied resemblances to figured specimens to which they might not be at all allied.

It is amusing to know how many of these very distinct species are made. Persons living in Australia, Madagascar, or various other localities, are requested by their acquaintances to collect and send them shells, to be submitted to the superior judgment of the home conchologist, who, of course, knows nothing about either their habits or the amount of variation to which they are liable. One set of varieties goes to America, and another to London, and we find two or three of the extreme variations described as distinct, whereas, if the necessary information had been forwarded by some intelligent naturalist, it would have been patent to everybody concerned that they were simply varieties of one variable shell. If Helix nemoralis were the inhabitant of some very distant land, at least a dozen very distinct species of it would appear in our books; they are very like troublesome weeds in a garden,-when once introduced, it is very difficult to eradicate them.

The N. dentifera, Powis, passes into the dark varieties of N. paupercula, Lam., the first from South America and the second from Australia.

Nassa delicata, A. Ad., N. cuvierii, Payr., vide N. variabilis, Phil., var. costata, Marr., and the small pale somewhat cancellated specimens of N. paupercula are very similar to some of the varieties of N. cuvierii, Payr.

N. nodifera, Powis, is intermediate between N. coronata, Linn., and N. canaliculata, Lam.

Another variety runs into N. stolata, Chem., and a curiously-coloured shell is so like the common European N. reticulata, Linn., that it is difficult to separate them.

The N. thersites, as figured by Quoy and Gaim, Voy. de l'Artrolabe, pl. xxxii., figs. 12–14, is an elongated variety of either N. globosa, Quoy, or N. thersites, Brug.

Another smooth form, with a thickened callous, connects it with the N. cornicula, Olivi.

N. compta, A. Ad., from Africa, is another variation of the N. cornicula.

Again, the cancellated callous shells of N. thersites, or marginulata, Lam., pass into the N. pulla and arcularia, Linn.

Strange as it may appear to the conchologists who have not studied this subject of variation, the N. gibbosula, Linn., is only a smooth form of the granular N. perlata, Meusch.

N. carmelii, Payr., is very closely related to, if it is not identical with, the N. gaudiosa, Hinds.

A small shell sent me a few days ago by G. H. Ponsonby, Esq., of London, was named by me some time ago, and is so like some of the small varieties of N. trifasciata, Gmel., that I am convinced these two forms merge into one at this point. N. acuticostata, Montr., is connected by means of some shells from Shark Bay, Australia, with the smoothlyribbed varieties of N. marginulata, Lam.

The broad shells of N. semigranosa, Dunker, show such a close connection with similar-sized specimens of N. pauperata, Lam., both of which are semi-transparent, that I am quite satisfied to place them as varieties of one species.

The fossil N. propinqua, J. Sow., from the Crag, is a cancellated variety of the N. semistriata, Brocchi.

N. algida, Reeve, is easily traceable into the N. canali culata, as figured in Reeve.

One of the most distinct shells, and one to which I could

at first see no alliance, has at length been brought into subjection, after a long struggle; it is a papillose variety of the N. glans, Linn. This discovery gives me the clue to a

number of other varietal forms.

This subject of variation of sculpture is not a mere theory, but may be confirmed by easily observed facts.

Neither the subject of variation, nor its occurrence among shells of the same species, may be considered to belong exclusively to modern times. In 1776, Da Costa, in his Elements of Conchology, at page 12, distinctly refers to this subject. Macleay, Lamarck, and Swainson, each endeavoured to give systems to account for the variable nature of the materials, and to try to direct the attention of naturalists to the study of affinity as a means to an end.

The author of the Vestiges of Creation endeavoured to counteract the vast tide of species-making, by showing that the materials upon which the naturalist was building his fixed distinctions were derived from other allied forms, and must of a necessity be ever varying. Mr. Darwin has done more in this direction than all the men living, or that have lived or gone before him; and it is sincerely to be hoped that a better state of classification will result from a study of variation than we find in that based upon the fixity of species.

The costa has its origin just below the nucleolar whorls, and is always present, even in shells that are otherwise smooth and highly polished, or in hyaline or young and transparent specimens. These ribs are always started either from the upper whorls, or from the upper part of the whorl; generally they commence at a tubercle, and become elongated in such a way, that we find all the intermediate lengths from the simple tubercle, until the rib is extended to the base of the whorl, showing its complete development. On the contrary, the striæ or sulci are nearly always seen at the