This shell is most likely Nodipecten pernodosus (Heilprin, 1887).
It was described in Explorations on the West Coast of Florida and in the
Okeechobee Wilderness; Transactions of the Wagner Free Institute of Science
Vol. 1, page 503 and illustrated as fig. 69.

A good description of the shell comes from Judith T. Smith. 1991. Cenozoic
Giant Pectinids from California and the Tertiary Caribbean Province:
Lyropecten, "Macrochlamis", Vertipecten, and Nodipecten species. US
Geological Survey Professional Paper 1391.

"Nodipecten pernodosus differs from N. fragosus, the Holocene species from
Florida and the Gulf of Mexico, in having a higher rib count (eight to
nine ribs instead of seven to eight), shorter hinge, and coarser
macrosculpture. Nodipecten pernodosus tends to have more ledges and
develops bulbous nodes on both valves...Nodipecten nodosus from the
Holocene of the Caribbean has the same rib count as N. pernodosus but not
the short hinge line or the tendency to develop nodes on right valves..."

It is found in the Caloosahatchee Formation; early Pleistocene.

Regards,
Charlie
******************************************************************************
Charlie Sturm, Jr
Research Associate - Section of Invertebrate Zoology
                     Carnegie Museum of Natural History, Pittsburgh, PA
Assistant Professor - Family Medicine

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