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Shells of two different species of sea snail: on the left is the normally sinistral (left-handed) shell of Neptunea angulata, on the right is the normally dextral (right-handed) shell of Neptunea despecta The shell of a large land snail (probably Helix pomatia) with parts broken off to show the interior structure.
Shell of marine snail Lunella torquata with the calcareous operculum in place Gastropod shell of the freshwater snail Viviparus contectus with corneous operculum in place. An operculum (Latin for 'cover, covering'; pl. opercula or operculums) is a corneous or calcareous anatomical structure like a trapdoor that exists in many (but not all) groups of sea snails and freshwater snails, and also ...
The columella is often only clearly visible as a structure when the shell is broken, sliced in half vertically, or viewed as an X-ray image. The columella runs from the apex of the shell to the midpoint of the undersurface of the shell, or the tip of the siphonal canal in those shells which have a siphonal canal. If a snail shell is visualized ...
The whorls of a snail shell usually overlap one another, forming a spire. Where the whorls overlap, there is usually a clear (if narrow) indentation. This indentation forms a visible line, which is continuous and reaches from the apex of the shell to the aperture; this line is the suture.
The central shell clearly shows the selenizone as a series of holes. A selenizone (from the Greek "selene" meaning "moon", and "zone" meaning "girdle") is an anatomical structure that exists in the shells of some families of living sea snails: the slit shells, the little slit shells and the abalone, which are marine gastropod mollusks from ...
Revolving lines – Spiral lines on a snail shell which run parallel with the sutures. [1] Rhombic – Having four sides, the angles being oblique. [1] Rhomboid – Four-sided, but two of the sides being longer than the others. [1] Rimate – Provided with a very small hole or crack, as some snails in which the umbilicus is very narrowly open. [1]
Retractive, when the markings slant backward from the suture; Bead - A small hemispherical protuberance resembling a bead, similar to but smaller than a nodule. Beaded - resembling rows or strings of beads. Cyrtoconoid spire - approaching a cone in shape, but with convex sides. Growth line - A fine transverse line marking the growth of the shell.
Astraea heliotropium, common name the sunburst star turban or the circular saw shell, is a large sea snail, a marine gastropod mollusc of the family Turbinidae, the turbans and star snails. [ 3 ] This large species was brought to Europe for the first time by the famous Captain Cook .