Good morning, Monterey Bay. This is an uncommonly accurate true natural cast of one of Santa Cruz's most iconic fossil species, Anadara trilineata, Purisima Formation rock layer, Santa Cruz, May 16, 2026, c. 3 million years ago. These rather rare reproductions form when an organism decays inside a sediment mold, and new sediment fills the empty space to create a natural perfect replica of the original shape. This particular species spent it's days living part in and part out of the sediment at the bottom of the ancient sea, filter feeding on microorganisms with its incurrent and excurrent siphons. Often, polychaete worms would take up residence by burrowing into the part of the shell that stuck out of the sediment, mooching a free meal on the water flow at the clam's siphons. Pacific Paleontology