Nonmarine Molluscan Remains from an Archaeological Site at La Playa, Northern Sonora, Mexico
Two hundred and sixteen molluscan shells, in four genera, from the upper cultural bearing zone of the La Playa site were studied as to environmental conditions under which they had lived. They showed cienega conditions ( marsh, pond, or sluggish stream) had existed. Some shells may have been redeposited from considerably earlier times.
Drake, Robert J.
"Nonmarine Molluscan Remains from an Archaeological Site at La Playa, Northern Sonora, Mexico,"
Bulletin of the Southern California Academy of Sciences:
Available at: https://scholar.oxy.edu/scas/vol59/iss3/3