During a dive I found these butter clam (Saxidomus gigantea) shells/valves still attached to one another in a protected bay. The valves have well developed concentric ridges that are parallel to the edges, and there is a large black external hinge ligament joining both valves together. The butter clam lives in sheltered areas with sand, mud or gravel substrates, and is commercially harvested for clam chowder. The siphon noticed above the substrate is white and the end is black, with many tentacles edging both openings. The butter clam can grow to 5.9 inches (15 cm) in length, with a range from the Southeastern Bering Sea to southern California.
References:
Cowles, Dave. “Saxidomus gigantea Deshayes, 1839” Invertebrates of the Salish Sea, Rosario Beach Marine Laboratory – a campus of Walla Walla University, 2005, https://inverts.wallawalla.edu/Mollusca/Bivalvia/Veneroida/Veneridae/Saxidomus_gigantea.html
Fretwell, Kelly and Starzomski, Brian. “Butter Clam, Saxidomus gigantea” Biodiversity of the Central Coast, University of Victoria, 2014, https://www.centralcoastbiodiversity.org/butter-clam-bull-saxidomus-gigantea.html
Jensen, Gregory with Gotshall, Daniel and Flores-Miller, Rebecca. Beneath Pacific Tides: Subtidal Invertebrates of the West Coast. Bremerton: MolaMarine, 2018.
