Tonicia forbesii Carpenter, 1857

Figures 2N, 12D–K, 13A–D

Distribution. From Mazatlán, Sinaloa, México to Taboga Island, Panamá Kaas et al. (2006).

Type specimens. According to Kaas et al. (2006) lectotype by designation of Keen (1958), BMNH? but not found.

Type Locality. Narborough Island, Noves Cove, Galápagos Islands .

Material examined. 40 specimens, maximum size of 40.5 mm long 23 mm wide. M (n=5); K (n=3); P (n=6); L (n=4); B (n=6); D (n=2); N (n=8); I (n=1); U (n=5).

Habitat. This species was found in two habitats: in the intertidal on the underside of medium-sized rocks, and in the shallow subtidal (3–6 m) in low wave energy areas on medium-sized rocks buried in sand. The juveniles were mainly collected in the subtidal on smaller rocks and associated with crustose algae. This species was found with C. lurida, I. muscarius and S. limaciformis .

Remarks. Tonicia forbesii was previously studied and reviewed by Thorpe in Keen (1971) and Kaas et al. (2006), who described the morphological characters of the valves and the girdle elements. Our SEM examination included aesthetes and radular teeth features, which revealed a conspicuous aesthete system. In some, the ocelli are scattered in the radial areas of the valves while, in others, they appeared aligned and arranged in groups of 2–4. The radular central teeth showed a small narrow almost imperceptible plate, and the minor lateral tooth is a long plate with a bilobed apex.