amykhenry's Identifications

A tiny limpet on side of gooseneck barnacle--see size 3rd photo.

Southern Finger Limpet (Lottia austrodigitalis)
"Apex near front, height moderate, anterior slope concave; to 30 mm long; radial ribs not pronounced on posterior (when present, square in x-sec, often beaded); brown to olive w. white checkering; shell highly variable. Southern species. Abundant, on rock (in Monterey), high to mid-intertidal zones; exposed & protected outer coast; also on plates of Pollicipes & on mussel shells. Geographic Range: Pt. Conception to northern Baja; southern Monterey Bay
Synonyms: Collisella austrodigitalis"

SEANET Hopkins Marine Station for Nearshore Plants and Animals of the Monterey Bay. Includes range of limpet species: https://seanet.stanford.edu/Limpets and https://seanet.stanford.edu/Limpets#austrodigitalis

"Lottia austrodigitalis is present from Bodega Bay, southward"
The Beachcombers's Guide to Seashore Life of California, J.D. Sept, Rev. ed. 2009, p. 77

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NOT

Rough Keyhole Limpet (Diodora aspera)
Greenish circular hole at the off-center apex. Dark, irregular vertical streaking pattern. Green foot.
"Ridges radiate from top and concentric lines cross the ridges at right angles. . . "

The Beachcombers's Guide to Seashore Life of California, J.D. Sept, Rev. ed. 2009, p. 73.

Rough Keyhole limpet. Diodora aspera: Shell is a tapered oval to 70 mm, triangular in profile; aperture at apex round, displaced slightly toward anterior. Radial ribs with weaker concentric sculpturing.

Common on rocks in subtidal & low intertidal. Feeds on encrusting invertebrates (sponges, bryozoans, ascidians) & algae.

https://seanet.stanford.edu/Prosobranchs#Diodora

A.k.a. Pacific Plate Limpet. Fine reddish brown bristles visible around foot. Gray to greenish in color with off-white rectangular blotches radiating from top of flat oval shell. Apex of shell is relatively low. Green algae are occasionally seeing growing on its shell.

The Beachcombers's Guide to Seashore Life of California, J.D. Sept, Rev. ed. 2009, p. 76.

Plate Limpet; head with golden tentacles; shell flat, broad to 60 mm long; smooth or with fine radiating riblets; apex at front third of shell, height low; anterior slope convex; color varies from tan, brown to gray-green; with checkered white spots or rays. Abundant, mid to low intertidal zones, exposed & protected outer coast. Geogr. Range: Bering Sea to Pt. Conception
https://seanet.stanford.edu/Limpets#scutum