Shell solid, very large, up to 106 mm. (4,125 inches) in length, broadly ovate, almost circular in outline, and roundly low-conical in profile, with the apex subcentral. Sculpture consisting of very numerous, narrowly rounded radial ribs, 58-76 primary, and a few secondary riblets in the interspaces of the lower half of the shell; margins finely crenulated. Colour, externally reddish chestnut, but almost invariably encrusted with algae and limy deposit; internally with a large ivory-white spatula, surrounded by a white callused area, and from there to the margin silvery, with the chestnut ribbing of the exterior showing through, especially towards the margin. Length 87-107 mm; Width: 81-94 mm; Height 33-45 mm.

Cellana talcosa (Gould, 1846). (Synonyms: Helcioniscus argentatus Sowerby, Edmondson, 1933; Patella argentata Sowerby, Pilsbry, 1891, non P. argentata Bosc, 1801; P. cuprea Reeve, 1854.) Length, 90 mm; diameter, 78 mm; height, 23 mm. Shell: domelike, inflated; apex near anterior third. Sculpture: fine radiating ribs that do not extend beyond the margin. Color: externally brown but usually covered with a growth of seaweed and/or barnacles, or a lime deposit; ribs brown; interior coppery; spatula white, often raised in older specimens.
These limpets are usually found below the low tide mark, at depths of 1 to 10 m; juveniles are occasionally found higher along the shoreline on coralline algae. This is the largest species of Hawaiian limpet, specimens reaching a length of 120 mm and a diameter of more than 90 mm. Pearls have been reported in these limpets on at least two occasions (Kay, 1967c).
Specimens of C. talcosa are common on Maui, Molokai, Lanai and Hawaii, but are not recorded from Oahu or the Northwest Islands and they are rare on Kauai.

Apart from large size, talcosa is distinguished by its nearly circular outline, broadly rounded, high-arched profile, very numerous, rather regular, radial ribs, and distinctive coloration, the exterior, when not encrusted, being reddish chestnut, and the interior silvery, with the scapula and surrounding muscle impression white. This species is found on exposed rocky shores and outer reefs near the low tide line.

Hawaiian Islands.