Southwest Florida Shells with Emphasis on Sanibel & Captiva
José H. Leal
(G.B. Sowerby I, 1825)
Saw-tooth Pen Shell
Shell size to 300 mm; shell similar to Atrina rigida, but more delicate. Surface sculpture of about 30 ribs bearing finer, smaller scales. Muscle scar inside nacreous area. Color translucent light-amber to light greenish-brown. This is the most distinctive of the three local species of Atrina. The supplementary image shows an individual in the Shell Museum "Live Tank." The bivalve is lying on its side (in nature it would assume a vertical position half-buried in the sand), and the incurrent aperture is on right and excurrent on left. The bivalve can "zip up" the mantle edges to regulate water flow.