Click the physiographic map to the right for fossils in other parts of Virginia
Untitled DocumentUntitled DocumentChama congregata
4.5 to 3 million years ago
This unique bivalve has asymmetrical valves: an attached bowl-shaped lower valve,
and a flat, round upper valve that acts as a lid that opens for feeding. This
species formed large reefs, or biostromes, during Upper Yorktown time that can
be as large as 14 feet thick. This species lives today in the Western Atlantic
from the southeastern U.S. to Brazil.