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Half-naked Pen Shell

Atrina seminuda

Markings and exact colorations may vary.

A pen shell with spiny ribs on one half and a smooth, bare lower half.

Typical size
5–9 in
How often it turns up
Uncommon
Collecting
Restricted

Empty shells are fine to keep on most public beaches. Live shelling is banned in Lee County and Florida state parks and needs a fishing license elsewhere — if an animal is inside, put it back.

Handling
Sharp edges

Thin edges break into sharp shards.

How to tell it apart

  • Large fan shape with a pointed hinge end
  • Radial ribs with short spines on the upper half only
  • Lower half smooth and nearly bare
  • Darker amber-brown than the saw-tooth pen shell

Where to find these in Florida

Beaches rated very good or excellent for shells. Each page shows today’s score, the best window and access details.

Found one?

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Commonly confused with

  • Stiff Pen ShellAtrina rigida

    The half-naked pen shell is smooth on its lower half; the stiff pen shell is ribbed throughout.

  • Saw-tooth Pen ShellAtrina serrata

    Half-naked is bare on its lower half; saw-tooth has scales over the whole surface.

More shells in the field guide

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