Maria’s Tegula Shell, Agathistoma mariana

Maria’s Tegula Shell, Agathistoma mariana. Shell provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, April 2018. Size: 1.3 cm (0.5 inches) in diameter.

Phylogeny: Maria’s Tegula Shell, Agathistoma mariana (Dall, 1919), is a gastropod mollusk that is a member of the Tegulidae Family of Top Shells. The genus Agathistoma is one of eight genera in this family, and there are twenty-five species in this genus.

Description: Maria’s Tegula Shells have a low profile, a circular outline, and consist of  four or five whorls. The shells exterior is sculpted by fine lines following the spiral with some of these lines being marked with fine nodes. The base has a waxy appearance and the umbilicus is deep. The exterior of the shell is gray to light brown in color, with reddish-brown mottling. The area around the umbilicus is green, and the interior is whitish. Maria’s Tegula Shells reach a maximum of 1.6 cm (0.6 inches) in diameter.

Habitat and Distribution: Maria’s Tegula Shells are found attached to, and under, rocks in the intertidal zone and to depths up to  20 m (65 feet). They are a subtropical to tropical Eastern Pacific species that are found in Mexican waters of the Pacific Ocean within the entire Sea of Cortez south to Guatemala. They have not been documented from the west coast of the Baja Peninsula.

Synonyms: Omphalius marianus and Tegula mariana.