. The animal kingdom : arranged after its organization; forming a natural history of animals, and an introduction to comparative anatomy. Zoology. 342 Div. 2. MOLLUSCA.—GASTEROPODES. Class 3. The Aquatic Pulmonea have only two tentacula. They come ever and anon to the surface to breathe, so that they can only inhabit waters of inconsiderable depth : thus thev live in fresh waters or in brackish pools, or at least near the sides and mouths of rivers. There are some amongst them without a shell: such is the Onchidium, Cuv.* A large fleshy cloak, of the shape of a buckler, overlaps the foot on ev
. The animal kingdom : arranged after its organization; forming a natural history of animals, and an introduction to comparative anatomy. Zoology. 342 Div. 2. MOLLUSCA.—GASTEROPODES. Class 3. The Aquatic Pulmonea have only two tentacula. They come ever and anon to the surface to breathe, so that they can only inhabit waters of inconsiderable depth : thus thev live in fresh waters or in brackish pools, or at least near the sides and mouths of rivers. There are some amongst them without a shell: such is the Onchidium, Cuv.* A large fleshy cloak, of the shape of a buckler, overlaps the foot on every side, and even covers the head when this is contracted. It has two long retractile tentacula, and over the mouth a veil, sinu- ated, or formed of two triangular compressed lobes. The anus and air-passage are under the hinder margin of the cloak, where, a little deeper, we find also the pulmonary sac. Near them, to the right, is the opening of the female organs, while, on the contrary, that of the male organ is under the right tentaculum ; and these two orllices are united by a groove wluch runs under and along the right edge of the cloak. Destitute of jaws, they have a muscular gizzard, succeeded by two membranous stomachs. Several species inhabit the coasts of the sea, but always in such a situation that they are uncovered at ebb tide, when tliey obtain the air necessary to respiration. The Aquatic Pulmonea, with perfect shells, have been placed by Linnaeus in his genera Helix, Bulla, and Valuta, whence they ought to be withdrawn. In Helix were the two following genera, whose aper- ture, as in Helix, had its inner [or pillar] margin protuberant and arcuate:— The Planorbis, Brug.,— Had already been distinguished from Helix by Bruguieres, and even previously by Guettard, because the whorls of their shell, rolled up nearly on a level, enlarge insensibly, and the mouth is wider than It contains a Snail with long, slender, filiform tentacula, at the inner base of w
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Keywords: ., bookauthorwe, bookcentury1800, bookdecade1860, booksubjectzoology
