lumachella

thumb|300px|Lumachelle samples from the Miocene of [[France, containing abundant bivalve individuals]]

Lumachelle (also known as lumacell, lumachel, or "lumachella") is a sedimentary rock containing partial to complete bivalve fossils that were accumulated by sedimentation. It differs from coquina (another fossiliferous sedimentary rock) in fossil preservation, as coquinas are mainly composed of small fragments of broken and crushed shells. Lumachelles may or may not contain complete bivalves including the shell, or alternatively only internal molds. While the term is mostly used for bivalve accumulations, other hard-shelled organisms can be occasionally encountered, such as gastropods.