Pinna bicolor,Bicolor Pen Shell, Common Razor Clam


These pen shells can reach a length of about 80–90 cm (31–35 in). They are characterized by thin, elongated, wedge-shaped, and almost triangular shells with long, toothless edges. The surface of the shells shows radial ribs over their entire length.

Pinna is distinguished from its sibling genus Atrina by the presence of a sulcus dividing the nacreous region of the valves, and the positioning of the adductor scar on the dorsal side of shells.

These bivalves most commonly stand point-first in the sea bottom in which they live, anchored by a net of byssus threads.