Physical characteristics

Vetigastropod shells range from squat and globe-shaped to elongate turreted structures. Limpet morphology has evolved at least six times in the vetigastropods; in many examples a semi-coiled component is still present in the early shell. Shell sculpture varies widely from simple concentric growth lines, which may be barely visible on the shell surface, to heavy radial and axial ribbing as well as everything in between. The shell aperture, or opening, is typically oval and often tangential to the coiling axis. Most species have an operculum (small lidlike organ) that is used to cover the aperture after the head and foot have been pulled back into the shell. The animals are supple and have a single pair of cephalic tentacles as well as a distinct snout containing the mouth. The lateral sides of the animal typically bear sensory

The species Bolma rugosa is relatively common in the Mediterrarean Sea. Its hard operculum is used to make beautiful gold jewelry since they keep their brilliant orange color for many years. (Photo by S. Pi-raino [University of Leece]. Reproduced by permission.)

epipodial tentacles. When present, copulatory organs are typically part of the right cephalic tentacle. The vetigastro-pod radula, or toothed ribbon that aids in feeding, is rhip-doglossate as in the Cocculiniformia and Neritopsina. The gills, kidneys, and hearts of many vetigastropods are bilaterally asymmetrical.

Vetigastropods range in size from the minute Scissurel-loidea and Skeneoidea, which may be less than 0.08 in (2 mm) long, to members of the Haliotoidea, which may be more than 11.8 in (300 mm) in length. External color patterns are typically drab, but such groups as the Tricolioidea as well as some Trochoidea and Pleurotomarioidea have bright color markings and glossy shells. Reddish shades are the most common. Many vetigastropod shells are iridescent because of the presence of nacre or mother-of-pearl on their inner surfaces.

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