GASTROPODA | CALYPTRAEIDAE |
Shells small to medium-sized, flattened, with an obsolete spire, an expanded aperture and a septum. The aperture matches the relief of the substratum on which the animal, very sedentar, is living. Inside glossy. |
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Calyptraea Lamarck, 1799:Shell conoidal, with a centered, vertical, pointed apex; primary sculpture of commarginal growth-marks; additional sculpture varying from none to buttons or scales; septum with helicoidal development, thin, with growth-marks. |
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Crepidula Lamarck, 1799:« Shell limpet-like, growing from a posterior apex or “beak” in a rapidly expanding, asymmetrical whorl, terminating in a wide aperture. Dorsal midline of the shell follows a right spiral […] Aperture occupies nearly the length of the shell. Columella modified into an internal septum extending across the posterior half of the shell. » – K. E. Hoagland: “Systematic review of fossil and recent Crepidula and discussion of the evolution of the Calyptraeidae”, Malacologia vol.16(2), Ann Arbor 1977, p.362. The species delineation can be given by the shape of the small muscle scar at the right side, the shape of the septal margin (straight, sinuous), the presence or absence of a second, smaller muscle scar on the left side, and also by the nature of the dorsal sculpture: smooth except growth lines (Cr. excavata etc.), or also with radial stripes as in some forms of Cr. incurva. The colours are also constant inside each species. |
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