Phascolosoma (Phascolosoma) nigrescens (Keferstein, 1865)  

This species is considered to be a widespread circumtropical species, inhabiting mainly soft and friable rocks, and crevices of dead coral boulders or buried in coarse sand. The main characters that distinguish this species from its congeners is the dome-shaped preanal papillae, and the exclusive clear streak expanded near the midpoint of the vertical and the middle of the horizontal portions of the hook visible when a hook is examined via transmitted light.