GOOSE BARNACLE
ON AN OIL CAN

The other morning on the beach I picked up a black, plastic container previously containing a quart of oil, and attached to it was the item shown below:

In the picture the shell's left side is attached to the can. If you flip the picture 90? counterclockwise the shell looks like a white butterfly with an orange rim along its upper wing. I felt sure that its name would be something like "Butterfly Barnacle" but when I showed it to a visitor she exclaimed "Oh, you've found a Goose Barnacle."

In an instant I saw what was goosy about it. As it's shown in the picture, doesn't it look like a goose's head, the broad, bulging area at the lower left being the cheek?

After the barnacle had been out of the water awhile, the slit between the orange rims opened a bit and a dark, spidery thing appeared. Those feathery items were the crustacean's modified legs, which in water beat rhythmically to draw plankton and detritus into the shell for consumption.

The barnacle lifecycle is complex, involving two larval stages. You can read about it and see pictures at http://en.wikipedia.org/wiki/Barnacle.

Goose Barnacles are LEPAS ANSERIFERA and they enjoy a worldwide distribution. They're crustaceans.