Genus with regular hexagonal reticulum of amber fibres.
Species fleshy spongy, with small low conuli. Colour deep yellow with brown or greenish (shallow water) tinge. Turns dark purple to black in air (aerophobic). Typical form (f. fistularis) consists of clusters of small tubes; f. ansa has more irregular tubes with short or fairly long (15 cm) and sometimes branching digital processes rising from the rim of the cylinder. Maximum size 30 cm.
Common in all reef and open lagoon environments, 1-6m;
f. fistularis only in outer reefs, 30-40 m.