Aplysia depilans. A. fasciata. A. punctata.
Shell dorsal, semicircular, of a thin yellow cartilaginous substance.
Closely allied to the Aplysia; it is a singularly formed shell, difficult to describe, as it contains few of the characteristics which distinguish other shells.
Shell rudimentary, entirely flat, sub-spiral, with a summit thick and very callous.
Base thick, callous, and sub-spiral; dilated above, thin, and wedge-shaped.
Lamarck has given a description of the animal of this genus, but only mentions that the scutcheon contains a shell or solid crustaceous body.
The animal belonging to this genus is furnished with a coriaceous shield, wrinkled.
Limax rufus. L. albus. L. cinerus. L. agrestis.
Shell external, very small, ear-shaped; very depressed, summit inclined posteriorly, not spiral; aperture oval, very large; the left edge sharp, a little rolled inward, especially behind.
_T. Haliotidea._ The Haliotis-shaped Testacella. Pl. 17, fig. 6.
Answering to the above description; very thin, transparent, and yellowish.
Shell proportionally very small, extremely thin, pellucid, almost membranous, oval or sub-globular; spire very short, of which the last whorl is very large; aperture large, semilunar; the edges sharp; the left edge arched, and extending itself interiorly to the summit.
_V. pellucida._ The pellucid Vitrina. Pl. 17, fig. 3.
Extremely thin, pellucid, and glossy; depressed, spire very short; aperture large and oval; colour pale yellowish green.
1. Helix. The Snail. One hundred and seven species.
According to the systematic arrangement of Lamarck, this genus now consists of shells with peculiar characteristic distinctions.
By Linnæus, marine, land, and fresh-water shells were united in this genus, and so confounded that the naturalist would often look in vain for the distinguishing characters which would enable him to class and determine the genus of the object under examination.
Notwithstanding the divisions of Lamarck, its species are numerous; the shells are terrestrial, and found in all parts of the globe; some are rare and beautiful.
The term Helix was given to this genus from the spiral form of the shell.
Shell extremely variable in form, generally globular, sometimes ventricose, conoid, never turriculated; summit constantly obtuse and rounded; aperture generally of a medium size, but sometimes very large or very small, always modified by the turn of the spire; oval, semilunar, more wide than long, edges disunited, entering but very little into the formation of the interior; the right lip or margin thickened or reflected.