Look like water filled pouches, can be quite firm to the touch. Two openings can often be seen, but will be tightly closed when out of water.

They live under rocky overhangs and under rocks from mid tide level down.

Filters small plankton out of the water column.

They may brood their young in their internal cavity. The larvae are known as tadpoles as they have the beginings of a backbone, a notochord.

References: Gordon D. P. (ed) (2009) NZ Inventory of Biodiversity; Vol 1 Kingdom Animalia. Canterbury University Press.