A thin external shell in brown wavy lines, with the green speckled animal folded up over it.
A cephalaspidean with an external shell of about 1 to 2 cm, thin, white and translucent, marked with three spiral brown bands crossed by fine wavy brown lines. The animal is far larger than the shell can contain: the head shield and the sides of the foot fold up and over it, and are dark green to olive, speckled with white and edged in a fine orange to blue line. Only part of the shell is visible on a moving animal.
The other shelled bubble slugs on the same ground are separated on the shell pattern. Hydatina physis, the rose petal bubble shell, is larger and marked with fine brown lines in a spiral only, without the wavy cross lines, and its mantle is rose to magenta with a paler margin. Bullina lineata is smaller and carries both spiral and axial red-brown lines on a white shell, giving a grid rather than a wave.
It is found mostly at night, on shallow sand, algal turf and fine rubble, and published feeding records are of small polychaete worms. Recorded from the shallows to about 20 m, and most sightings are in the first few metres.
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.
