\Por"pi*ta\, n. [NL., from Gr. ? brooch.] (Zo["o]l.)
A genus of bright-colored Siphonophora found floating in the
warmer parts of the ocean. The individuals are round and
disk-shaped, with a large zooid in the center of the under
side, surrounded by smaller nutritive and reproductive
zooids, and by slender dactylozooids near the margin. The
disk contains a central float, or pneumatocyst.