It is not to be disputed that the discoveries which have taken place among the vermes of those testaceous bodies since the time of Linnæus, have introduced us to a far more extensive acquaintance with the beings of this nature than Linnæus could have possessed. The term Limax, which Linnæus applied not only to the animal inhabitants of the Voluta family, but also to the Buccinum, the Strombus, the Murex, the Trochus, the Turbo, in short to almost every genus of the Univalves, and some even of the Bivalves could not fail to excite remark. It could scarcely be conceived that in the very ample range of the creation which those genera embraced, such uniformity could prevail, and the subsequent observations of various Naturalists have tended fully to assure us that the Linnæan character of the animal inhabitants of the testaceous tribes was much too vague and comprehensive. There are indeed, it must be confessed, a considerable number of those testaceous bodies, the animals of which are still unknown, and may possibly so remain, but forming our conclusions, from the great multitude that has been recently discovered, and the number of those which have been examined with anatomical attention, we may presume, with safety, that the Linnæan Limaces ought properly to be divided into several distinct genera. How far a methodical distribution of the shells themselves, founded upon the zoological distinctions of the animal inhabitants, may be admissible in our cabinets appears less certain. The greater number of those shells, of which the animals are totally unknown, present insuperable objections; and the attention of collectors in the formation of the Conchological Cabinet, so rarely extend beyond the more obvious characters which the structure of the shells present, that we can scarcely deem it practicable.
The animal of the shell before us, Voluta pyrum, has been ascertained and well described by Lamarck, De Montfort, and other writers; it has the head armed with two obtuse feelers of a club-like form; the eyes advanced and placed at the base, at the outerside of those feelers; the mantle or fleshy covering terminating in an elongation folded into a kind of tube above the head; the foot, or disk, strong and muscular, and armed with a small round horny operculum.
According to the Linnæan classification, the shelly covering of this animal is a Voluta; and so far as the most prominent criterion of the Voluta genus, the folds or plaits upon the pillar lip be considered, this character is unequivocal. Linnæus regarding this as one of its most essential definitions, has overlooked the differences that prevail in the structure of the spire and beaks, or includes them only as distinctions of the different families into which his Volutæ are divided. Later writers differ upon this subject; these differences are considered by many as generical, and thus the Linnæan Volutæ have become separated into several distinct genera. In the shell before us, the beak is lengthened or produced, and canaliculated; and thus constitutes in the classification of Lamarck, a species of his Turbinella; and is the shell in particular which he adopts as the type of that genus. The character of that genus, as proposed by this Conchologist, in his work entitled Animaux sans vertèbres, is thus expressed, Turbinelle (Turbinella) a shell turbinated or subfusiform, canaliculated to the base, and having upon the column from three to five plaits or folds of a compressed form and placed transversely. Murex scolymus of Martini, Voluta ceramica of Lister, and Voluta capitellum of the same author, are comprehended with the Linnæan Voluta pyrum in this genus Turbinellus.
It has been observed by De Montfort that Lamarck has made a group of those shells which accord with the above character, and which he himself adopts with some small variations: according to this writer, the genus Turbinelle, of which our Voluta Pyrum is considered as the type, has the shell heavy, univalve, with an obtuse spire ending in a nipple; the mouth sloping and lengthened; the pillar denticulated with large equal folds or plaits, the outer lip strait and cut off, and the base lengthened.
After all the pains, however, which Lamarck and other Continental Naturalists have taken to establish the genus Turbinella, Cuvier in his Règne Animal observes that the shells of this genus differ in no other respect from the Conic Volutes than in the prolongation of their opening, forming a kind of canal, and adding that it is not easy to trace the limits between the one and the other.
We have experienced some surprise in observing that while so much attention has been bestowed by writers upon the generical distinctions of Voluta Pyrum, the differences that prevail in its presumed varieties have almost entirely escaped attention. It should be remarked that in the Gmelinian constitution of this species there are no less than four distinct varieties, all which, according to Gmelin, and subsequently to other writers, appertain to the Linnæan species Pyrum. From the synonymous references which Lamarck has brought together in one view, it is obvious that his opinion is the same; his Turbinella Pyrum, which is the same as the Linnæan Voluta Pyrum, will be observed to comprehend the several presumed varieties of the species to be found in the works of Martini and Chemnitz, and the same is again observable in the works of Denys de Montfort. There are, however, some Conchologists in England who do not agree in this particular, for they constitute at least three distinct species of the presumed varieties of Voluta Pyrum. This division of the species was first proposed by Dr. Solander, and has been subsequently adopted in several of our English Cabinets. As the particulars of this arrangement may not prove unacceptable, we shall proceed to describe them.
To the first of these new species Dr. Solander retains the Linnæan name of Voluta Pyrum, it is that kind which has the beak elongated, and is known by the familiar name of the Long Beaked Turnip Shell. This is the Voluta rostrata of some Conchologists; Rapum rostratum of the Colonnian Museum; and inhabits the seas of Tranquebar.
As the preceding shell is distinguished by the name of the Long beaked Turnip Shell, in allusion to the elongated structure of the beak, there is another known by the appellation of the High Spired Turnip Shell, in reference to the greater elevation of its spire; this is a second species of Solander, and is called by him Voluta Ponderosa; in the Calonnian Museum it stood under the name of Rapum productum. This shell inhabits the seas of Madagascar, and is the kind which becomes the more immediate object of our consideration as the subject of our present plate.
The third kind of Turnip Shell is from the straits of Malacca, a shell more ponderous than the preceding; of a broader form and having the spire more depressed. This is the common Heavy Turnip Shell of our English Cabinet, Voluta gravis of Solander.
These distinctions proposed by the late Dr. Solander are found conformable, in a particular degree, with the classification observable in the cabinet of M. de Colonne. The shells of M. de Colonne, it appears, were thus arranged by the celebrated Conchologist M. Favanne. They have, nevertheless, we believe, passed unnoticed by any of the modern writers upon this subject. The distinctions are certainly obvious, and might probably fully authorize their separation into species: it must be at least admitted that as varieties of the same species they are strikingly distinct.