Tends to grow in a single plane like a Sea Fan (which it is not) rather unlike the other common black coral in the area, the Bushy Black Coral (q.v.). Branches and secondary branches grow pinnately. The secondary branches are those that carry most of the polyps, which radially deploy their translucent tentacles. Rather than black, branches are lighter in colour, ranging from orange to dark brown.

Unlike other corals, stony in particular, Black Corals do not form polyp coralites as such, with polyps each developing a system of radial tentacles. These do contract when needed, but cannot completely retract within the branch structure.

NOTE: Black Corals owe their name to the fact that their branches exsude a dark coloured protein, which builds up in successive concentric layers.