[1] The black murex shell is commonly found in the Gulf of California (Sea of Cortez), in the Western Mexico.

[2] These sea snails can be found in the intertidal and subtidal waters, with sand and gravel substrate, at depths up to 60 m.[3] Shells of Muricanthus nigritus can reach a length of 75–200 millimetres (3.0–7.9 in).

The shell surface bears short spikes around the body whorl and spire.

[citation needed] This species is quite similar to Hexaplex radix.

The shells of these two species mainly differ in the length, width and in the proportion of black versus white.