Sea Butterfly

Corolla moves through the water by flapping a wing plate nearly twice the size of its gelatinous shell, giving it the nickname “sea butterfly”.
(@ 2012 KJ Osborn, Smithsonian )

Unlike many other kinds of free-swimming sea snails, Corolla does not have a hard shell. Instead it produces a gelatinous shell—the bumpy slipper-shaped structure surrounding its body. The animal moves through the water by flapping a wing plate nearly twice the size of its gelatinous shell, giving it the nickname “sea butterfly”. Corolla catch their prey by producing a mucus net many times the size of its body, and waiting while plankton and other organic material become entangled. See more images of mid-water creatures in our slideshow.