GENUS LYMNMA.
Shells subovate, oblong, or somewhat tapering. Aperture entire, longitudinal. ly oblong, the right lip joined to the left at the base, and folding back on the pillar.
Observ. These shells, as well as those of the preceding genus, were placed by LinnzUs with his Helices, but they offer characters sufficiently distinct, particu larly.their inhabitants.
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1. L. Catase' opium. Shell thin, horn co loured or blackish ; whorls four or five, the first large, and generally the remain der darker and rapidly decreasing to an acute apex, and wrinkled across ; aper ture large, oval,' not three-fourths the length of the shell.
Length seven-tenths of an inch; breadth nearly one half of an inch.
Inhabitant yellowish, sprinkled with small, often confluent, paler dots; tenta cula two, broad, pyramidal ; eyes black, placed at the base of the tentacula ; tail obtuse rounded or emarginate, not so lotug as its shell.
Plate 2. fig. 3.
It is with much hesitation that we adopt a new specific name for this shell, having always heretofore considered it as the same with the L. Putris of authors, (which has b een, perhaps,mistaken for the Helix Limosa of Linne.) as far as we can as certain, the principal difference appears to be in the more oblique revolution of the whorls in the European species, and the more abrupt termination of the spire.
Inhabits the Delaware river and many other waters of the United States, in con siderable numbers, and may he foiind plentifully, during the recess of the tide, about the small streams through which the marshy grounds are drained, in com pany with several other shells. When kept in a vessel of water, like others of its kind, it will proceed not only up the sides of its prison, but also along the sur face of the water, the shell downward, with regularity of motion and apparent ease ; in this case the reverted base of the animal is concave ; and as the surface of the water is compelled to a corres ponding concavity, the pressure of the atmospheric column will account for the sustentation of the animal (whose specific gravity is much greater than that of the water)in this singular position: It occasion ally crawls to the margin of the water to inhale a supply of air ; with this object the foramen is protruded to the surface, and opened with an audible snapping sound, similar to that produced by the resilience of the nib of a pen.
There is a species of this genus that we have named L. Jugularis ; and which, in
consequence of its hating been found but once, must be considered as a doubtful inhabitant of the United States. It may he thus described. Shell tapering; whorls about six ; suture not deeply impressed ;' aperture hardly equal to half the length of the shell, but little dilated ; within browAish, particularly upon the column, whic is contracted in the middle ; outer lip white, and almost imperceptibly re pand within ; umbilicus very distinct. Length one inch.
A specimen was also brought from the West Indies by Mr. L'Hermenier of Charleston.
2. L. Heterostropha. Shell sinistral, sub ovated ; colour, pale yellow, chesnut or blackish ; whorls four, the first large, the others very small, terminating rather ab ruptly in an acute apex ; aperture large, somewhat oval, three-fourths of the length of the shell, or rather more ; within of a pearly lustre, often blackish ; lip a little thickened on the inside, and tinged with dull red.
Inhabits with the first species, and al most as numerous.
Plate 1. fig. 6.
Animal resembles that of L. Catasco plum, but is of a darker colour and longer than its shell, the tentacula also are long er, and setaceous ; tail acute.
The mantle is trifid at the base of the pillar lip, and at the upper corner of the aperture ; deposits eggs the beginning of May; eggs enveloped by a transparent gelatinous substance; the nucleus, after a few days, appears of a pale or milk white colour, and not so well defined as those of L. catascopium.
3. L. columella. Shell thin, fragile, horn-colour; whorls four, longitudinally wrinkled. Spire prominent, acute. Su. ture not much impressed. Aperture di lated, ovate. Columella much narrowed near the base, so that the view may be extended from the base almost to the in terior apex of the shell. Length seven. tenths of an inch nearly ; of the spire one quarter of an inch.
Inhabits stagnant waters and miry places.
Journ. Acad. Nat. Sciences, vol p. 14.
Animal aquatic, base not so long as the aperture ; dusky, with small whitish spots; tentacula broad, pyramidal, compressed ; eyes small, black, placed at the inner base of the tentacula.
This species is allied to L. Catascopium but the revolution of the whorls is more oblique, the shell thinner, the aperture much more dilated, and the columella dif. ferently formed. For several specimens of this shell, we are indebted to Mr. Titian Peale.