Placopecten clintonius pelecypod from the Yorktown formation of Virginia

This shell was among a number of Chesapectin jeffersonius specimens and it caught my eye due to the difference. A little research leads me to believe that this is a Placopecten clintonius pelecypod as it exists within the Yorktown formation at the same horizon as C. jeffersonius. The shell is smaller than C. jeffersonius and the radial ribs are both more numerous and finer.

This specimen came from the Yorktown Formation, which is Neogene in age (Pliocene epoch, Zanclean stage), along the James River in Virginia.