This deep-water group, though widely distributed, has not previously been recorded from New Zealand. The familial characters include the following features:

Abactinal surface roofed over by a membrane, supported by the elongated paxillae, enclosing a supradorsal brood-chamber, within which the eggs develop. Water is drawn in through numerous small pores on the actinal surface and expelled through a central opening on the abactinal surface, termed the osculum.