The Interesting Iridescent Pen Shell

pen shells
Pen Shells Found in Florida

Pen shells (family Pinnidae) are usually gray or brown in color with an iridescent sheen.  They are long and tapered in a triangular shape and most of the ones I’ve seen were on the east coast beaches in Florida.

They can be huge!  My resource book says up to thirty-one inches in length!   But many are found broken since they are a bit more fragile than an ordinary seashell.

The varieties found in Florida  include the Saw-toothed pen shell, Stiff pen shell and Amber pen shell.  The ones pictured here (photo by me) look like saw-toothed as they are smoother than the Stiff pen shell  which has ridges with spines.  Amber pen shells are lighter in color (hence the name).

Flag pen shells are wide and rounded on top and are found in the Indio-Pacific region.

The Noble Pen Shell (Pinna nobilis) has an unlikely history. It’s byssal threads (which anchor the shell in the sand when alive) were once used to make fabric. The threads were woven together to make what was known as “sea silk”. This large shell is found in the Mediterranean region and is in danger of extinction due to over use, pollution and decline in places for it to survive.

The Whelks of Florida

The Whelk shells of Florida are widely collected and they can be some of the largest shells you’ll find on Florida beaches. (Don’t collect them if they are inhabited.)

The Knobbed Whelk (Busycon carica), Channeled Whelk (Busycon canaliculatum), Pear Whelk (Busycon spiratum) and Lightning Whelk (Busycon contrarium) can all be quite large – the Pear is the smallest.  Common characteristics include their long shape with a wide opening down the length of the shell.

Of these four, the Pear Whelk is the smallest when full grown. It grows to a length of 5 1/2 inches. I have come across pear whelks out on the sandy flats while boating. I’ve seen them as yellow, gray and with brown splotches. They are usually inhabited by hermit crabs.  Then I recently found one with a live snail inside. (2nd photo)

pear whelk seashell
Pear whelk seashell with hermit crab inside
pear whelk mollusk
Pear Whelk with Mollusk Inside

The Lightning Whelk is another one I find often in the backwater areas. It’s usually small like the pear whelk, but this one can grow to be 16 inches long.  It is recognizable by it’s left-side opening.

lightning whelk mollusk shell
Live Lightning Whelk (Notice the left-sided opening)

This is a fairly new photo of the knobbed whelk. I discovered it in January just offshore on an island in the Indian River backwater. A hermit crab was living inside, so I got some photos and returned it to the water.

knobbed whelk
Knobbed Whelk

The channeled whelk is not a shell I have found in one piece. It grows to be 7.5 inches in length. The top spiral part of the shell differs from the other whelks because it looks extended, like someone pulled it out. The whorls on the other shells are tight and semi-flat.

large broken whelk shell
White and broken channeled whelk shell remains

This is the only channeled whelk I have found and even though it was very broken it turned out there was a hermit crab living in it! I had to take it back and return it to the water.

The Channeled whelk only lives along the northeastern coast of Florida to about halfway down the state.  I guess that explains why I don’t see many of this kind of shell.

Latest from the Blog

Quiet Day On The Boat

A hot and beautiful day on the boat took us to a remote river island, a stop in the ocean, and then to Ponce Inlet.

A Huge Sanibel Whelk Found on Easter

I did not find this whelk shell (on the link provided), but I have started following a blog written by a lady (pam) who is lucky enough to actually live on Sanibel Island on the gulf coast of Florida and she is the one who found the foot long whelk shell.

Her blog is so wonderful – one of the best I’ve seen – and since she goes shelling just about every day, in the 3rd best place in the world to do so, she has tons of info and photos of shells on her blog.

Please don’t leave me! But do check out her blog.

Just click here and see her fabulous whelk and other ocean creatures.

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