Colour is no help at all; the squared head shield and the hunting are what identify it.
A headshield slug to about 6 cm, smooth and roughly cylindrical, with a broad squared shield over the head, two short rounded lobes at the rear and no visible shell. Colour is extraordinarily variable — black, blue-black, olive-green, orange-brown or cream, plain or speckled — and animals from one stretch of sand can look like different species. Shape places the genus; the species within it are separated on internal anatomy, and a photograph will often not settle a name.
It hunts other cephalaspideans, following mucus trails across the sand and swallowing prey whole with the shell intact, usually Haminoea bubble shells and smaller headshield slugs. It ploughs just below the surface of fine sediment, and the raised trail is generally seen before the animal at the end of it.
Recorded from the shallows to about 20 m on fine sand and silt.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
