[Hydromedusae] Small tentacle-like organs situated on the umbrella margin between the true marginal tentacles, devoid of swollen marginal bulbs and solid.
Two types are generally found: 1) spiral cirri which coil spirally and have a terminal cluster of cnidocysts, which are the most common (e.g., Gneus Mitrocomella) (Bell margin 5); 2) flexile cirri, which are straight, not coiled, and having the cnidocysts in rings (ex Cosmetira) (Flexile marginal cirri).
Cirri may be immediately adjacent to the marginal bulbs and are then termed lateral cirri (e.g., Eucheilota maculata) (Bell margin 2); they may also occur along the umbrellar margin in the inter-spaces between marginal tentacles, in which case they are called marginal cirri (e.g., Phialopsis) (Flexile marginal cirri).

[Cephalopoda] Arm cirri are elongate, fleshy tendrils along the lateral edges of the oral surface of the arms, especially in cirrate octopods. Body cirri are fleshy protuberances of skin that can be erected as papillae, usually dorsal to the eyes.