Small mollusc with a thin transparent external shell.
Shell is inflated with wide aperture and is fragile.
Cephalic shield flattened without tentacles but with
two posterior flaps covering the anterior part of the
shell. Parapodia are short and do not cover the
middle part of the shell. Foot extends beyond the
posterior part of the shell. The colour of the mollusc
is a variable brownish camouflage-like but mottled
with white, red-brown and black spots. Dark
varieties including almost black specimens have been
seen. In shallow water on algae.
Specific characteristics:Small size and short
parapodia are used to distinguish this species from
the related H. navicula.