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The mission of the San Mateo County Historical Association is to inspire wonder and discovery
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Object Record

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Catalog Number 2014.009.026
Description Lucinoma annulata, ringed lucine fossil dating from between 1.5 million years ago to .75 million years ago commonly found at low tide in littoral (sandy and muddy bottom) or sub-littoral (open bay, muddy marine) zones. Fossil specimen is mostly intact, with top and bottom shell still attached at ligament. Specimen is light brown in hue, with darker brown sediment exposed between shells. Growth rings are easily visible along the outer edges of top shell. Bottom shell has reddish-hued patches scattered throughout, likely indicating the presence of iron oxide.
Object Name Shell, Animal
Collection 3D - Paleontology
Title Lucinoma annulata, Ringed Lucine Fossil, 1.5-.75 Ma
Date 1.5 - .75 Ma
Kingdom Animalia (Animals)
Phylum Mollusca (Molluscs)
Class Bivalvia (Bivalves)
Order Veneroida (bivalve order)
Family Lucinidae (Saltwater clams)
Genus Lucinoma
Species annulata
Inscription Text none
Provenance Fossils taken from Merced Formation collected at Westborough Boulevard at Highway 280 in the late 1970s or early 1980s. (See Yancey 1978, Fig. 2: Artifacts taken from E Stratified Section/D-5929). Most specimens (especially clams) in this collection are not extinct and can still be found in the Bay Area.
Notes Retired Geologist Ken Lajoie identified on 4/24/2014.
Lucinoma annulata (Common name: Ringed Lucine) are nearly symmetrically round, with a point in the center. Shells feature ridged rings, which are added annually. This species still thrives in the Bay Area.
Dimensions H-1.5 W-2.75 D-2.875 inches
Search Terms Fossils
Merced Formation
Shellfish
South San Francisco
Subjects Fossils
Marine biology
Shellfish
Shells