Rough pen shell

Pinna rudis

Family Pinnidae - pen shells

Bivalve (2 shells); shell wedge or fan-shaped, slightly inflated, very fragile, translucent, beak pointed; color pinkish orange; hinge area long, straight; low, broad, rounded ribs, sometimes with scaly projections; interior with nacreous (shiny) layer, divided by a shallow groove longitudinally, the dorsal lobe of the layer is longer than the ventral lobe.
Similar Species
Similar to the amber pen shell, P. carnea, but the amber pen shell is narrower and the ventral lobe of the nacreous layer is slightly longer than the dorsal lobe. Other pen shells do not have a divided nacreous layer.
Gulf, attached to hard surfaces.
Maximum Size
56.5 cm (22 1/4 in)
Other Common Names
Rude pen shell
Previous Scientific Names
Has been found at Stetson Bank near the Flower Gardens Banks. Specimens in the photographs were found attached to a buoy rope that washed ashore at Surfside Beach, TX.