Cut-Ribbed Ark (Anadara floridana): Each Rib Incised

The Cut-Ribbed Ark is a sturdy 3- to 5-inch-long white bivalve, with a dark brown periostracum (a furry-looking covering over part of the shell). The beaks or umbones of each valve are low and incurved. The hinge line between the two valves is fairly straight. There are between 30 and 38 curved radial ribs which widen as they approach the margin (outer edge) of the shell. The two halves of the bivalve are slightly unequal in size.

The indentifying feature (to help differentiate this Ark shell from some in the same family which look similar) is the fact that the ribs are each incised with a longitudinal groove. (This “engraved” line is less evident, of course, in worn shells, such as those which often are found on beaches.)

This Ark lives in moderately shallow water from North Carolina to Texas, and near the West Indies.

Notes

The shells pictured here were found at Myrtle Beach, South Carolina.
For more information on the Cut-Ribbed Ark see:
- R. Tucker Abbott and Percy A. Morris, Peterson Field Guides: Shells of the Atlantic & Gulf Coasts & the West Indies.
- Carol M. Williams, Beach Bountiful: Southeast.
Classification: Family Arcidae; Superfamily Arcoidea; Order Arcoida; Superorder Prionodonta.
Scientific nomenclature is subject to change, due to ongoing research. The above classification coincides with that published by the Conchologists of America, Inc.
Digital formatting is by Jonathan Mitchell.

Cut-Ribbed Ark:Groovy!

Notes

Cut-Ribbed Ark:
Groovy!