Norris Top Shell, Norrisia norrisii

Norris Top Shell, Norrisia norrisii. Underwater photograph taken in coastal waters of the greater San Diego, California area, May 2018. Photograph and identification courtesy of Bob Hillis, Ivins, Utah.

The Norris Top, Norrisia norrisii (G.B. Sowerby I, 1828), is a gastropod mollusk that is a member of the Tegulidae Family of Tops. They are also known as the Norris Shell. The shell is solid, wide, and circular in profile, with a very low spire and a smooth external surface. The exterior of the shell is brown with black on the base near the umbilicus and the columella (area between the umbilicus and aperture) is green. The living animal is reddish-orange. Norris Top Shells reach a maximum of 6.7 cm (2.6 inches) in diameter.

Norris Top Snails are found on hard substrate and within brown algae, especially giant kelp, from the lower intertidal zone to depths up to 36 m (120 feet). They utilize kelp stalks for protection to avoid predation. They arrange range from Central California to Asuncion Island Baja California Sur.

A synonym is Trochiscus norrisii.