Shell oval, conical, apex a little in front of the middle. Surface having rather coarse low ribs. Dark border of the inside very narrow, or reduced to a series of dark scallops. Prominent characters of this species are the erect, conical form, rather wide coarse, ribs, and the narrow margin of the inside, usually not continuous but composed of scallops or square spots.
The variations may be classed under two main groups
a. Typical pelta: Rather large, solid, strong, with low coarse ribs, almost obsolete, or visible only posteriorly. Central dark spot of the interior rather small or wanting. Grayish-white, with numerous radiating black stripes, often divaricating or broken into a tessellated pattern.
b. Form cassis: the ribs become stronger. Solid, strong, having stout radiating ribs about 25-27 in number, those in front narrower or obsolete. Dark spot of the inside small or obscured ; margin with a mere dark line, or a series of scallops between the ends of the ribs. Outside dull, grayish.

Lottia pelta is a eurytopic, polytypic species. More than 5 ecological variants (forms) have been reported (see McLean, 1966; Jobe, 1968). Because of the difficulties encountered in identification of this species, individual diagnostic descriptions are given for each of the forms known to occur in San Francisco Bay. The forms are based only on shell characteristics and habitat preference. Radular and animal characteristics are the same for all forms and are therefore presented immediately following the individual form descriptions.
Typical form : Shell. Medium to high profile; apex positioned in the anterior third of shell. All slopes convex. Sculpture of heavy radial ribs or nodules, equally developed on all surfaces. Aperture anteriorly narrowed. Color gray to black with or without white markings. Interior margin narrow, may be streaked with white; intermediate area blue-white; interior stain brown, irregular or completely lacking. Length, 20-45 mm.
Habitat: Middle to low intertidal; commonly found under the alga Fucus and on substrates with dense macroalgal cover.

Small, smooth specimens (<10 mm) occur on the trochid gastropod Tegula funebralis (A. Adams, 1845). This trochid gastropod is typically the host of the acmaeid Lottia asmi. Differentiation between the 2 species is based on the color of the interior intermediate areas. In C. pelta the intermediate area is blue-white, and in C. asmi the intermediate area is glossy black. Other smooth, small specimens commonly occur on the algae Fucus and Iridaea. These limpets are typically brown in color, both exteriorly and interiorly. Larger specimens of L. pelta are distinguished from specimens of Lottia digitalis by the development of the radial ribbing. In L. pelta the ribbing is equally developed on all slopes, while in L. digitalis the ribbing is strongly developed only on the posterior slope and is weaker on the lateral and anterior slopes.

Northeast Pacific. Aleutian Is. and south coast of Alaska to the Santa Barbara Islands, California. Middle to low intertidal; commonly found under the alga Fucus and on substrates with dense macroalgal cover.