[Radiolaria Polycystina] In Spumellaria: elongate projections (usually 3) radiating from a central subcircular disc in the shells of some Spongodiscidae. Arms can consist of unstructured spongy meshwork (spongy shell 4), or of spongy meshwork with more or less clearly visible chambered rings (spongy shell 5).

[Cephalopoda] The eight circumoral appendages in coleoid cephalopods (Ce 1E, Ce 1Y). One pair of modified appendages called tentacles lies between the ventrolateral (3rd pair) and ventral (4th pair) arms in cuttlefishes and squids; one pair of modified, greatly reduced appendages, called retractile filaments, lies between the dorsal (1st) and dorsolateral (2nd) arms in Vampyromorpha.