Muricopsis octogonus, or the octagonal murex, is a species of medium-sized sea snail, a predatory marine gastropod mollusc in the Family Muricidae, the murex snails or rock snails.
This subspecies is endemic
to New Zealand
. It is found along the east coast of the North Island
south to East Cape
This muricid is found from low water level to depths of up to 70 m
The shell is solid, and narrowly fusiform
with strong rounded axials, crossed by prominent closely spaced spiral cords. At points of sculptural intersection, the cords, to a varying degree, develop spinose processes. In littoral shells the spines are usually poorly developed, but in deep water examples they are often long, hollow and recurved or upcurved. When viewed from above the shell is octagon-shaped.
The shell coloration is light to dark brown.
The maximum shell height is 60 mm, and width 32 mm.