Spisula catilliformis - a bivalve. These fossil surf clams were collected just north of San Francisco Bay. Polinices sp. - a gastropod. These fossil moon snails are from Contra Costa County. This is a representative fossil of the larger crab found in the diatomite.
Whole crabs are approximately ten centimeters across.
Pinnixa galliheri - a small crab. Pinnixa galliheri - a small crab. In this remarkable fossil, two crabs are preserved right next to each other, with one on its back. Detail of the joins in the chitin plates of the exoskeleton are visible.