CONUS Generalis,

Flambeau Cone.

Generic Character.—See Pl. 65.

Specific Character.

C. testâ gracili, fuscâ, fasciis albidis strigis undatis longitudinalibus interruptis ornatâ; spiræ productæ apice acuto, anfractibus concavis, lævibus; basi nigrâ.

Shell slender, brown, with white bands, interrupted by longitudinal stripes; spire produced, the tip acute, whorls concave, smooth; base black.

Conus Generalis. Gmelin, p. 33. 75. var. a. Dillwyn, 359. var. a. Martini, vol. 2. p. 58. f. 645, 646. (dark variety) f. 648 to 652. (pale varieties). Gualt. 20 f. G.

Conus Generalis. Brug. p. 642. Lam. Ann. vol. 15. p. 363.

It becomes necessary to figure this elegant, but not uncommon Cone, in order to show the young conchologist the little importance that should be attached to colour in the discrimination of species: the figures will likewise point out more fully the distinctions between the present shell, C. maldivus, and C. cinctus; three species, whose close affinity require illustration.

These relative distinctions may be comprised in a few words; they rest principally on the spire, which in C. generalis has the upper half much lengthened, slender, and acuminated: in C. maldivus the spire is thick and much shorter: the whorls in both these species are quite plain, and nearly flat: the spire of C. cinctus resembles the last in form, but is deeply concave and striated. These characters are, I think, very satisfactory as specific distinctions.

On the other hand, some attention to these shells lately, has convinced me that many of the species formed both by Bruguiere and Lamarck should be more correctly considered as varieties; inasmuch as their specific distinctions rest, for the most part, on colour alone: this appears, indeed, to be the leading character selected by these eminent conchologists, and to which, therefore, they have attached the greatest importance. From this opinion, however, I completely dissent; on the principle, that no character which is variable can, with any consistency, be made use of to express permanent distinctions, when not supported by peculiarity of formation or sculpture. The great art in framing the description of a species consists in singling out those characters alone which are most permanent, and exist in every variety of that species; for, when once a character is found to be variable, it no longer becomes a distinction by which a species can be recognised. I consider, therefore, formation and sculpture as the only certain characters of species, and that variation of colour should alone distinguish varieties.

It is therefore not surprising that the specific characters given by MM. Bruguiere and Lamarck, and resting principally on the colours of these shells, are frequently obscure, and always long; two inevitable evils attending every attempt to describe minutely the colour, form, and disposition of the markings of shells. In justice, however, to these great naturalists, it should be observed, that in this attempt they have done that best which no writer has ever done well.

The spire of C. generalis is generally spotted, and the white band on the margin of the body whorl, more or less crossed by broad waved stripes of a dark brown. It is an inhabitant of many parts of the Indian Ocean.

Pl. 119

AMPULLARIA globosa,

Round Apple Snail.

Generic Character.—See Pl. 103.

Specific Character.

A. testâ globosâ, lævissimâ, olivaceâ; spirâ depressâ; aperturæ margine crasso, fulvo, sulcato; umbilico parvo, contracto, juxta basin posito; operculo testaceo.

Shell globose, very smooth, olive; spire depressed; margin of the aperture thick, fulvous, grooved; umbilicus small, contracted, placed near the base; operculum shelly.

Helix Ampullacea. var. Gmelin, p. 3626. no. 43. Chemnitz, 9 tab. 128. fig. 1133. 1134. p. 105.

This is the most common of the two shells of this genus, which have their mouths closed by a shelly operculum. It is well described by Chemnitz, and his figures are very tolerable; yet, like all the authors of that period, he considered it as a variety of Helix ampullacea. From all these supposed varieties it is, nevertheless, quite distinct; the spire is more depressed than that of any other species, and the umbilicus is placed near the bottom of the inner lip: the whole shell is very smooth, and, although generally of a uniform yellowish olive colour, is sometimes marked by narrow bands of purple brown. The margin of the outer lip is slightly reflected, and the colour, beneath the epidermis, almost white. It is a native of the rivers of India.

From the remarks on this genus, made at Plate 103, the fact of their opercula being either shelly or horny, is sufficiently established. These formations, however, there is every reason to suppose, may generally be detected by the following indications. In such species as have a shelly operculum, the margin of the aperture is thickened all round, and has a parallel internal groove for its reception: the probable use of this groove I have detailed elsewhere. On the other hand, in those species which are known to have horny opercula, this margin and groove do not exist; and that part of the shell which is between the top of the aperture and the umbilicus, is thin and unprotected. This latter formation is by far the most frequent, and leads to the conclusion that the majority of these shells have their opercula horny.

On the distinctions between this genus and Planorbis, little need be said. The principal difference consists in the latter having no operculum; but another, and a very remarkable one, (which seems to have escaped all writers,) is, that the shells of the latter genus are destitute of any columella. The Planorbis cornu-arietis of Lamarck, has been removed by Mr. G. Sowerby to this genus. This shell, it is true, appears to be intermediate between one and the other; but the only affinity which it bears to Ampullaria, is in the oval form of the aperture; while it is allied to Planorbis by its discoid form, want of the columella, and being universally described as without an operculum: the preponderance of evidence is clearly in favour of the situation originally assigned to it by Lamarck.

The characters, therefore, given to the genus Ampullaria by Mr. G. Sowerby, will be found incorrect. There was no necessity for explaining, much less for altering, (in this instance,) the masterly definitions of Cuvier and Lamarck. With regard to the second species given by Mr. Sowerby to illustrate this genus, he is no less in error; for the real A. rugosa, of all authors, is a strikingly distinct shell from that which he has figured under this name. This will be sufficiently obvious by referring to the figures either of Lister, Chemnitz, or Lamarck.

Having offered these remarks on a subject to which I have paid some attention, I wish to refrain from pointedly noticing other errors and misconceptions into which Mr. G. Sowerby has fallen; rather wishing that greater experience, and more matured judgment, may lead him to do this himself, prior to the publication of the system of Conchology which he has announced.

GENERAL ALPHABETIC INDEX

OF

LATIN AND ENGLISH NAMES

TO

VOLUME II.

SYSTEMATIC INDEX.

VERTEBROSA.

PART II.

ORNITHOLOGY.

SYSTEMATIC INDEX.

ENTOMOLOGY.

PART II.

SYSTEMATIC INDEX.

CONCHOLOGY.

PART II.

ADDENDA ET CORRIGENDA.

In the Systematic Index to Vol. I. Conchology, Part I., for "Acephalis" read "Acephali;" and at the head of the list of errors, for "Corregenda" read "Corrigenda."

NOTES