Family Mactridae

Shell size to 130 mm; shell triangular-ovate, with large, central umbones. Chondrophore spoon-shaped, well developed in adults, reduced in juvenile stages. Sculpture absent, except for fine growth lines. Periostracum olive-brown. Color dirty-white to cream-tan. Live in sand. (Additional photo represents a juvenile specimen from Bunche Beach in Lee County.)

Measuring up to 50 mm (about 2 inches), Rangia cuneata (also known as Gulf Wedge Clam) is a brackish water bivalve native to the Gulf of Mexico. The shell is heavy, whitish, and normally covered with a thick brown periostracum. As with most species of the family Mactridae, the ligament is internal. Capable of withstanding very low water salinities, the species has invaded estuaries of the East Coast of the US and northern Europe. The species is found locally in the Caloosahatchee estuary, where it thrives upstream almost to Lake Okeechobee. The shell in the main image was collected in 1958, by Dale Stingley, in La Belle, Hendry County, Florida. The additional image shows unpaired valves collected in 2019 by Lorin Buckner, under the Caloosahatchee River’s Midpoint Bridge (between Fort Myers and Cape Coral.) All photos by Patricia Starkey.

Shell size to 18 mm; shell small, triangular, inflated. Umbones on center of valve. Shell surface smooth, except for radial ridge on posterior region. Hinge with small chondrophore. Color white to yellowish-white. May resemble juvenile surf clam, Spisula raveneli.

Shell size to 49 mm; shell thin but strong, oval, compressed. Posterior region with two ridges, beyond which shell gapes. Color white, with strong grayish-brown periostracum.