Two heads, both active! :-O Could not decide which way to go, as both heads seemed to have different opinions ;-) Video: https://www.flickr.com/photos/30314434@N06/51709342856/in/dateposted/
Notch on posterior end. About 1/3" long. On a black turban snail in this photo, but moved onto kelp too.
A couple of rogue individuals in a protected overhang ≈12m depth
Fish for sale at Lomami River crossing. This observation is for the lower fish.
Archive photo, previously with date mislabeled.