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The mission of the San Mateo County Historical Association is to inspire wonder and discovery
of the cultural and natural history of San Mateo County.

Object Record

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Catalog Number 2014.009.022
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 of a top shell embedded in sediment. Shell is somewhat flat and nearly symmetrical. Growth lines are visible from underneath sediment coating the shell. Rosy-colored hue is likely from iron oxide present. Underside surface is dark brown, with reddish patches throughout.
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-1.375 W-2.125 D-1.875 inches
Search Terms Fossils
Shellfish
Merced Formation
South San Francisco
Subjects Fossils
Shells
Shellfish
Marine biology