The Half-naked Pen Shell

Pinnidae - Wikipedia

American Stiff Pen Shell (Atrina rigida Lightfoot, 1786): Byssal Threads

The Saw-tooth Pen Shell

Stiff Pen Shell: Atrina rigida (Lightfoot, 1786)

Observations on Pearls Reportedly from the Pinnidae Family (Pen Pearls)

M-650 PEN SHELL, Atrina rigida or A. serrata - Gulf Specimen Marine Lab

Atrina seminuda - Wikipedia

The Baggy Pen - Bailey-Matthews National Shell Museum

Pen shells have a tremendous potential' – Meghan McCoy

STOBOK 300 Pcs Pen Case Pen Shells Empty Pen Barrels Black Pens Ballpoint Black Gel Pen Black Pen Shell Empty Pen Shell Gel Pen Holders Empty Pen-holders Replaceable Ballpoint Pen Refill