The black murex shell is commonly found in the Gulf of California (Sea of Cortez), in the Western Mexico in the intertidal and subtidal waters, with sand and gravel substrate, at depths up to 60m. 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. Moreover shells of H. nigritus are more oblong and show more spines in black. Feeds primarily on clams.