Monterey Formation : Invertebrates

A large number of fossil invertebrates have been found in the Monterey Formation. The majority of these are near-coastal species, primarily bivalves, gastropods, and crabs.

The best preservation of crabs has come in diatomite deposits, while our best fossil molluscs come from concretionary sediments.

Mollusca : Bivalvia and Gastropoda

Arca sp. - a bivalve.

This genus includes fossil ark clams. These particular fossils were collected in Monterey County, California.

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.

Arthropoda : Crustacea

Unidentified crab

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.

These tiny "pea crabs" have been found in large numbers, both as intact preservations such as this one, and in numerous fragments.

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.