The roughly cylindrical body has four longitudinal ridges giving it a square cross section and a flat base.

The leathery body wall is reinforced by calcareous spike-like structures which in this species include basket-shaped spicules and perforated ellipsoids.

There are three rows of red tube feet on the underside and the body tapers at the posterior end, the anus being surrounded by 5 tooth-like projections.

[4] Colochirus quadrangularis is found in the tropical Indo-Pacific region at depths down to about 115 metres (377 ft).

It is a suspension feeder, rearing up its anterior end up and spreading its feathery tentacles to catch phytoplankton and other organic particles.