Stiff Pen Shell
Atrina rigida (Lightfoot, 1786)
I've collected a number of Stiff Pen Shells complete or nearly complete. Most of the Pen shells are broken up when they reach the beach. Oftimes you'll find on the reflective tip (ssee below).
Stiff Pen Shells (S. Hutchinson Island (November 2020)
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American Stiff Pen Shell:
Strength and Rigidity
By Patricia B. Mitchell.
The American Stiff Pen Shell may reach a length of 1 foot. (Some types of Pen Shells grow as long as two feet, and occasionally contain black pearls.) The American Stiff Pen Shell has 15-25 radial rows of fluted or tubular spines, or scales, on its smoky dark olive-brown surface. Though the shell is almost translucent and looks rather fragile, it is actually fairly strong. The interior of the shell is irridescent. The living clam inside has a bright golden-orange mantle. Often a small, commensal crab lives inside the mantle cavity, and frequently various types of snails and chitons reside on the exterior surface of the Atrina rigida. The bivalve lives in soft sand or mud anchored by its byssus, a tuft of silky filaments which protrudes from the beak of the shell. The American Stiff Pen Shell may be found on beaches from North Carolina to the West Indies.
A “golden fleece” was made from the byssal threads of the 14-inch Giant Mediterranean Pen Shell. In 1931 Julia E. Rogers wrote about this industry:
Long ago it was spun and woven into cloth by the people of Mediterranean countries, where Pinna nobilis is abundant. Robes of marine silk were much desired articles of commerce, under the name “tarentine.” A pair of gloves could be folded away in a walnut shell, and a scarf of considerable size in a snuff-box, so fine and supple were the delicate threads.
Fishermen, especially off the Sicilian coast, rake these mollusks off the rocks in considerable quantities. The byssus is torn off and sold to country women who wash it with soap and card it. In this crude process, much is lost. The threads are spun and woven into fabrics so soft as to rival the finest silks.
Nowadays this cloth is manufactured in Palermo and Lucca, but chiefly for its rarity. Shawls, scarfs, gloves and stockings, may be seen in great exhibitions as high examples of textile art.
Also, since ancient times, people have used Pen Shell meat as food. (The creature is closely related to the mussels, though the meat [actually the muscle] is said to be similar to that of the scallop.)
Notes
The shells pictured here were found at Myrtle Beach, South Carolina.
For more information on the American Stiff Pen Shell see:
R. Tucker Abbott, American Seashells.
S. Peter Dance, Eyewitness Handbook of Shells.
Carol M. Williams, Beach Bountiful: Southeast.
Classification: Family Pinnidae; Superfamily Pinnoidea; Order Pterioida; Superorder Eupteriomorphia; Subclass Pteriomorphia.
Scientific nomenclature is subject to change, due to ongoing research. The above classification corresponds to that published by the Conchologists of America, Inc.
Digital formatting is by Jonathan Mitchell.