longer than wide. This shell had been placed by Linnæus among the Helices, under the name of Helix haliotoidea; and by Muller among the Bullæ, under the name of Bulla velutina; but Lamarck seems very properly to have disposed of it under a distinct intermediate genus between the Ne

rites and the ear-shells.

Stomatia. Is a genus which has been formed by Helblins and Lamarck from a shell, which had been placed under the genus Haliotis, but which wanted the holes, which exist in the shells of that genus. Argonauta. A very thin, single chambered univalve shell; the spire concealed in the internal part of the shell.

Concholepas. An oval univalve, convex in its superior part, with its summit obliquely inclined upon the left edge; the cavity simple; two teeth and a sinus at the base of the right edge. Dargenville and others had placed the shell of this genus among the Patellæ ; but Bruguìere having seen several with tendinous opercula, disposed them under the genus Buccinum. Lamarck has however thought fit to consider it as forming a genus, connecting the Patella with the other spire valved shells.

Nerita. A semiglobular univalve, flattish beneath, not umbilicated at the spire; the opening semicircular the columella or partition, nearly transverse. Lamarck has retained in this genus only the imperforated Nerites; the others he transfers to the next genus. The Nerites have not only no umbilicus but no true columella, having in its place, a simple partition; which is flat, thin, and longitudinal, originating in the groove of the first spire, and generally dentated.

Natica. This genus of Lamarck's is characterized by a nearly globular shell, umbilicated at the left lip with a callosity at the umbilicus; the opening semicircular; the columella oblique, and not dentated.

Helicina. This genus is founded by Lamarck on a shell figured by Lister (Plate LXXI. fig. 59) and which he describes as a globular shell; the opening entire, semioval; columella with a callus, compressed inferiorly; an operculum. The propriety of this adoption cannot be judged of, from merely the figure of this shell in Lister's work.

Helix. An orbicular or elongated univalve, with an obtuse or concave spire; the opening entire, forming a half moon. Lamarck divides the shells which have been hitherto disposed under this genus into

eight genera. 1. Bulimus, an oval or oblong shell, the opening whole, longer than wide; the columella smooth, without folds, truncature or widening at the base; as in Bulima hæmastoma. 2. Lymnæa, an oblong subturriculated shell, longer than wide; opening entire, the inferior part of the right edge, turning up and passing into the opening, and forming a very oblique fold on the columella; as in Helix stagnalis. 3. Melania, a turriculated shell; the opening entire, oval or oblong, widened at the base of the columella; Helix amarula is of this genus. 4. Ampullaria, a globular bellied shell, umbilicated at its base, no callosities on the left lip; the opening entire, longer than wide. Helix ampullacea forms this genus. 5. Planorbis. A discoid shell, the spire flattened or sunk, not prominent, the opening entire, longer than wide, and filled up laterally by the convex projection of the last turn but one. The type of this genus is Helix planorbis. 6. Haliotidea. 7. Ianthina. 8. Helix, a globular shell, with a convex or conoidal spire; and particularly with the opening diminished by the projection of the last turn but one; but as this last character is common to the Planorbis also, these two genera are evidently confounded. The separation which is hereafter made of some shells which originally were in the genus Helix, in agreement with the ideas of Bruguìere, will be, therefore, more correct.

Volvaria, a cylindrical shell, twisted on itself, without a projecting spire; the opening narrow, as long as the shell; one or more folds on the base of the columella. This genus was formed by Lamarck from a shell which is figured and described by Pennant, vol. iv. Plate LXX. fig. 85. He considers it as intermediate between Bulla and Bulima.

Bulla. A tumid shell, the spire not projecting; the opening as long as the shell; no umbilicus. This genus of Linnæus has been much reduced by Bruguìere, who placed several species under Bulima, and established his genus Ovula. Lamarck has still further reduced them, by forming the genera Terebellum, Pyrula, Ampulla, and Achatina.

Ianthina. This genus is formed by Lamarck on a single shell described by Lister, Brown, Forskal, and other naturalists; which derives its claims of distinction from Helix, not so much from the character of the shell as from that of the animal, which differs in its structure materially from the animal of the Helix, since it is furnished with a curious apparatus, being an inhabi.

tant of the sea, for swimming, instead of that for crawling, with which the Helices are provided. It is nearly globular, and almost diaphanous; the opening is nearly triangular, with an angular sinus at the right edge.

Turritella. This genus was formed by Lamarck, for the reception of those shells which Linnæus had placed in the last section of his genus Turbo, as Towers; and which Dargenville and Favanne had considered as screws. The characters of the genus are, a turriculated shell; the opening round, whole, but having a sinus at the right edge.

Cyclostoma. This genus was formed by Lamarck for the reception of the Wentletrap, and other shells of the same character. The propriety of thus forming a new genus is rendered evident by the doubts which had arisen respecting the placing of it in any old genus. Linnæus having considered it a Turbo; Rumphius, a Buccinum; Dargenville, a Screw; and Davila, Gualteri, Guettard, and Favanne, merely a Tube, from its not possessing a columella, which they considered as essential in a univalve shell. The shells of this genus differ in their forms; their openings are nearly round, and their sides connected circularly. The shell is formed of seven spires, separated by a void space; with ten or twelve longitudinal ribs, which uniting, form a rim round the lip. These ribs externally supply the place of a columella.

Bulimus. A globular, oval, or turricu lated shell, the opening of which is entire, not grooved at the base, and always longer than wide. This genus of Bruguiere comprises some of the shells considered by Linnæus as Helices and Bullæ ; and the genera Auricula, Pyramidella, Melania, Lymnæa, Agathina, Maillot, and Bulima, of Lamarck. The essential character distinguishing this genus from Helix is the opening being longer than it is wide.

Turbo. A conoidal or turriculated shell; the opening entire, round, without any tooth; the edges disjoined on the superior part. Several shells which were reckoned by Linnæus of this genus have been removed from it by Bruguìere, and placed under his genus Bulima, and others have been taken from it by Lamarck, and disposed under the genera Cyclostoma and Turritella.

Trochus. A conical univalve shell; the opening almost always quadrangular, flattened transversely; the columella oblique.

Lamarck has divided this genus into four: 1. Trochus. 2. Solarium, with an open, umbilicus, or crenulated opening on the inside of the spiral turnings, as in the Trochus perspectivus. 3.Monodenta. The opening rounded, and furnished with a tooth formed by the truncated and projecting base of the columella, as in Trochus labio, Linnæus. 4. Pyramidella; the columella projecting, perforated at its base, and possessing three transverse folds, as in Trochus dolabratus, Linnæus.

Cerithium. A univalve turriculated shell, the opening terminated at its base by a short, narrow canal, either suddenly turning backwards or truncated, but never grooved out. In this genus of Broguìere are comprehended several shells from the genera Trochus, Strombus, and Murex of Linnæus. The shells differ from those of Murex by their turriculated form; and from the screws, in not having the groove at the base of the canal.

Pyrula. A subpyriform shell, canaliculated at its base; without any projections, and having the belly part nearer to its summit than to its base; the spire short; the columella smooth; the right edge without a groove. Lamarck founding the distinction on the situation of the bellied part of the shell, and on the greater or less length of the spire, has formed two new genera; one with those shells possessing this character of the genus Bulla, and the other of the genus Murex, calling the former Pyrula and the latter Fusus.

Murex. An oval or elongated univalve shell, generally foliated, plaited, spinous, or tuberculated; the opening always prolonged into a canal, running straight, or turning directly backwards, and always entire. In the earlier stages of their growth it is diffi cult to separate the Murices from the Strombi. Lamarck divides this genus of Linnæus into five genera. 1. Murex, with tuberculated or spinous projections, and channelled at the base, as M. ramosus. 2. Fusus; fusiform, without projections, with the bellied part either equally distant from the extremities or nearest to the base; spire elongated; columella smooth; right edge without groove, as M. colus. 3. Fasciolaria; nearly fusiform; no projections; with two or three very oblique folds on the columella; and channelled at the base, as in M. tulipa. 4. Pleurotoma: fusiform or turriculated, without projections, and having a groove, or sinus, near the summit of the right edge, as in M. babylonicus. 5. Cerithium, already described.

Rostellaria. Lamarck has formed this genus on Strombus fusus, (Linnæus) and on some fossil species found at Courtagnon. The characters of the genus are: a fusiform shell, terminating inferiorly by a canal with a pointed beak; the right edge entire or dentated; dilated more or less in a wing, according to age, and having a sinus contiguous to the canal.

Strombus. A bellied univalve, terminating, at its base, by a canal, accompanied with a distinct sinus; the right lip dilating, or spreading itself out, with age, in a simple or digitated lobe. Lamarck divides the genus Strombus of Linnæus into three. 1. Strombus; terminating in a short canal, truncated or grooved out; the right edge dilating, with age, into a simple entire wing or lobe; with a sinus distinct from the groove at the base, as in S. pugilis. 2. Pterocera; a bellied shell, terminated inferiorly by an elongat ed canal; the right edge dilating, with age, in a digitated wing, and having a sinus near its base, as in S. lambus. 3. Rostellaria, the genus last described.

Buccinum. An oblong or oval shell, the opening of which is terminated at the base by an oblique groove, without any sensible canal, or external border. Bruguìere has divided the Buccina of Linnæus into the genera Buccinum, Terebra, Cassidæa, and Purpura. Under the genus Buccinum are therefore here comprised tumid shells, with from three to ten spiral turns; a summit generally flattish; a surface rarely even; the predominating colours dull; the lip extended more or less in a bow, and rarely jagged.

Cassidæa. A tumid shell, the opening longer than wide, terminated at its base by a short canal, recurved towards the back of the shell; the columella plaited in the lower part. This genus of Bruguìere is intended to comprise the helmets (casques) of Gualteri, Klein, and others.

Terebra. A turriculated univalve; the opening grooved in the lower part; the base of the columella twisted or oblique.

Purpura. Au oval shell, generally with spines, or tuberculated; the opening terminating in a very short canal, the extremity of the canal grooved out, the base of the columella finishing in a point. The shells included in this genus by Bruguìere, are not those species which have been hitherto considered, as Purpuræ, by Dargenville and others, and which belong to the genus Murex; but those species which appear to connect the genus Buccinum and Murex. The openVOL. VI.

ing of these shells is rather large, oval, round, upwards, and more contracted in the inferior part; the right lip has but little thickness, and is grooved or notched ; the left expands with a wrinkled ridge, which terminates in the groove.

Voluta. A cylindrical, or oval, univalve shell, grooved out at the base, but without a gutter; the opening longer than wide; and the columella plaited. The division of this genus by Linnæus is very clear and useful; but Lamarck proposes a still nicer distinction of the shells of this genus, by dividing them into eight genera. 1. Voluta, an oval shell, more or less bellied, summit obtuse or mammillated; the base grooved, but without a gutter; the columella with several plaits, of which the lowest are largest and longest; as in Voluta musica. 2. Oliva, sub-cylindrical, grooved at the base; the turns of the spire separated by a channel; the columella striated obliquely, as in Voluta oliva. 3. Ancilla, oblong, a short spire, base of the opening hardly grooved; a swelling, or oblique roll, at the base of the columella. 4. Mitra, fusiform or turriculated, spire pointed at the summit, the base grooved out, without a gutter; the columella with plaits, the lowest being the least, as in Voluta episcopalis. 5. Columbella, marked by a swelling on the internal face of the right edge; as in Voluta mercatoria. 6. Marginella, the right edge emarginated, as in Voluta vespertilio. 7. Cancellaria, the right edge grooved internally, and the base of the opening almost entire, as in Voluta reticulata. 8. Turbinella, sub-turbinated, canaliculated at its base, with transverse plaits on the columella.

Ovula. A tumid shell, more or less elongated at the extremities; the edges rolled inwards; the opening longitudinal, not dentated on the left side. This genus is formed by Lamarck from shells, which had been comprised by Linnæus in his genus Bulla. The shells of the genus Ovula differ from those of Cypræa, chiefly by the absence of teeth from the left-side. Bulla volva, ovum, spelta, verrucosa, and gibbosa, of Linnæus are placed under this genus.

Terebellum, a shell nearly cylindrical, pointed at the summit; the opening longitudinal, narrow upwards, and hollowed out at its base; the columella truncated. This genus is formed by Lamarck, of the Bulla terebelum of Linnæus, which he has removed from the genus Bulla, and has placed in this genus, as intermediate between the Ovulæ and the Olives.