Key to species of Hincksia
| 1 | Intertidal, in rope-like strands, cells of filaments isodiametric to twice as long as broad, hook-like or short lateral branches present; plurilocular organs about as long as broad | H. breviarticulata |
| 1 | Subtidal, not rope-like, cells becoming larger than twice their diameter, without hooklike lateral branches; plurilocular organs cylindrical more than twice as long as broad attached alternately or adaxially | H. mitchelliae |