Pacific Jewel Box (variant), possibly a False Limpet or Rock Oyster fragment
Phylum: Mollusca, Class: Bivalvia, Order: Venerida, Family: Chamidae, Genus: Chama, Species: Chama buddiana · Chamidae (Jewel Box family) · Bivalve (Single Valve). This is the upper (right) valve of a sessile bivalve, characterized by its irregular, flattened, disk-like shape.
Species
Chama buddiana (Confidence: High for the region and morphology)
Shell Type
Bivalve (Single Valve). This is the upper (right) valve of a sessile bivalve, characterized by its irregular, flattened, disk-like shape.
Family
Chamidae (Jewel Box family)
Size
Approximately 1 to 1.5 inches (2.5 - 3.8 cm). This is a juvenile or smaller-sized specimen, as adults can reach 2-3 inches.
Color & Pattern
Predominantly chalky white to off-white exterior. The center shows some residual brownish-orange staining near the umbo (beak). The interior is likely nacreous white. The color appears somewhat sun-bleached and worn by surf action.
Rarity
Common for the Cabo region. These are frequently found on rocky beaches but are often overlooked due to their encrusting nature and resemblance to rock fragments.
Habitat
Attached to hard substrates such as rocks, pier pilings, or other shells. Found in intertidal and shallow subtidal zones in tropical and subtropical waters.
Geographic Range
Eastern Pacific, specifically from the Gulf of California (Cabo San Lucas) south to Peru.
Description
A robust, thick-walled bivalve valve. The exterior surface is rugose with faint radial ribbing and evidence of leafy or scaly growth lamellae that have been worn down by wave action. It has an irregular sub-circular outline and a flattened profile typical of the upper valve of a stationary species.
Key Features
Single flattened valve; irregular growth rings; thick calcified structure; central brownish discoloration at the apex; lack of a distinct spiral usually found in gastropod limpets.
Collector Value
Minimal monetary value ($1-$3). It is a common 'beach find' specimen. Its value lies in its use as a geographic marker for the Cabo San Lucas intertidal zone.
Condition Notes
Fair to Good. The shell shows significant beach wear (abrasion), which has smoothed the diagnostic leafy spines usually present in 'Jewel Boxes.' Small bore holes suggest past predation by sponge or predatory gastropods.
Interesting Facts
Jewel Boxes are called 'sessile' because the bottom valve grows cemented to a rock, making them look like part of the reef. They are 'left-handed' or 'right-handed' depending on which valve attaches to the substrate.
Ecological Role
Filter feeder that cleans the water column of plankton. They provide micro-habitats for smaller organisms that live among their leafy scales when the shell is alive and attached.
Similar Species
Pododesmus macrochisma (False Oyster) which has a hole in the bottom valve; various Acmaea limpets, which would have a more symmetrical conical peak.
Beach Finding Tips
Look in rocky tide pools and along the drift line after high tide in Cabo. They often look like flat white pebbles until flipped over to reveal the smooth interior.
Notes
Cabo