The five slender arms taper to a point and consist of a number of articulated joints each topped by an oval plate wider than it is long.

The color of this brittle star is grayish-brown or reddish-brown, with a paler patch at the outer end of the radial shields.

[2] Amphiodia urtica is native to the west coast of North America, its range extending from Alaska to Mexico.

It occurs on muddy bottoms where it immerses itself in the sediment, raising its arms into the water above to catch food particles floating by.

A polychaete worm, Malmgreniella lunulata, sometimes lives on the arms and a copepod sometimes inhabits the stomach.