[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.

[Cnidaria] In hydromedusae, marginal cirri are small tentacle-like structures found on the umbrella margin between the true tentacles;
— spiral cirri are the commonest kind, coiling spirally and bearing a terminal nematocyst cluster itself slightly spiral;
— flexile cirri, as found in Cosmetira, do not coil and have the nematocysts in rings;
— lateral cirri are those situated beside a tentacle bulb (see bulb), as in Eucheilota maculata.

[Polychaeta] A cirrus is a sensory appendage which is usually slender and cylindrical.

Alternative form for cirri : cirrus.