Fossil moon snails: top left is Miltha xantusii, specimen 3153-23882 Top right and bottom are Polinices, specimens 4185-67325. Found in Chula Vista.

Modern moon snails: top left is P. lewisii Upper right is P. draconis Bottom is P. recluzianus. Found in California.

Polinices sp. cf. P. lewisii
Lewis' moon snail
Naticidae

Time
Pliocene Epoch

Description
A few hundred species of moon snails live along the coasts of the world in sand from the low intertidal to deep water. They are carnivorous snails that feed on bivalves by boring holes in the shells of their prey. The bore hole of a moon snail can be recognized by its relatively large size and the neat, beveled edge of the hole (see the bored fossil clam, Miltha xantusii in the photograph). Moon snails have an impressively large foot that nearly covers their shell and helps them plough through the sand in search of clams. The egg capsules of moon snails are deposited in a circular sand collar.

Naticid fossils are found in our area in deposits as old as the Cretaceous. Fossil Polinices recluzianus have been reported in abundance from the Oligocene to Recent. However, fossil moon snails may be very difficult to identify because worn or disintegrated specimens of California species very closely resemble one another. Moon snails collected from Pliocene-age deposits in San Diego are most likely Polinices lewisii. This species lives on sandy, subtidal bottoms along the southern California coast. In the Pacific Northwest this species is more common and may be found living nearer to shore (close to the low intertidal zone). In southern California, Polinices recluzianus is common and sometimes found live at low tide on sandy beaches. The geographic range of this species extends no further north than Ventura County. This species is common in Pleistocene age deposits. Shells of modern Polinices draconis, a deep water species, are sometimes found after storms, but they are often broken or beat up. This species is rare in the fossil record.