[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.

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

Moreover, shells of H. nigritus are more oblong and show more spines in black.