Dark-shouldered snake eel
The dark-shouldered snake eel ( Ophichthus cephalozona , also known commonly as the headsaddle snake eel , the black-neck snake eel , the blacksaddle snake eel , or the one-banded snake-eel ) is an eel in the family Ophichthidae ( worm/snake eels ) . 
<triplet> Ophichthidae <subj> eel <obj> parent taxon