Half-naked pen shell

Atrina seminuda

Family Pinnidae - pen shells

Distinguishing
Characteristics
Bivalve (2 shells); shell wedge or fan-shaped, slightly inflated, very fragile, translucent; beak pointed; color tan sometimes with purple-brown markings; hinge area long, straight from beak to posterior end of shell; 10-15 radiating ribs (smooth or with tubular spines) on upper (dorsal) portion of shell; ventral portion usually smooth with no ribs; ventral margin of shell curved at posterior end; interior muscle scar well below edge of nacreous (shiny) layer.
Similar Species
Has less ribs and larger spines (if present) than the saw-tooth pen shell. Similar to stiff pen shell, but interior muscle scar on thestiff pen shell borders the edge of the nacreous layer.
Habitat
Gulf and bay, sandy to muddy bottoms
Maximum Size
23 cm (9 in)
Other Common Names
Previous Scientific Names
Comments