(Ritter and Byxbee, 1905)
Soft, limp, cylindrical colonies; ribbon-like in flattened condition (Pyrostremma agassizi). Transparent, with red zooids. Size up to 47 cm long and 5 cm in diameter (Van Soest, 1981). Open end of the colony provided with 4 short quadrangular processes (Pyrostremma agassizi 1), which are easily lost (cf. Van Soest, 1974c). Closed end of the colony sharply ridged. Ascidiozooids as long as high, with a smoothly curved endostyle (Pyrostremma agassizi 2).
Collected in South Atlantic Ocean: Pyrostremma agassizi M