The Bullinidae contains a single genus, the Bullina. They possess an external shell which is inflated in appearance, providing a capacious interior into which the animal can completely retract. It is thin-walled and lighter than that of the acteonids with a shorter spire. It can be closed off with a thin operculum. The shell attains a maximum size of 20 mm.
The shell is well calcified with a short, sometimes depressed, spire. It is sculptured with spiral grooves for its complete length. The aperture is large and rounded anteriorly, and narrows posteriorly.
There is a small umbilicus and a straight columella. The white or cream coloured shell usually bears a distinctive pattern of markings consisting of red, brown or black bands or lines following the spiral sculptures, and may also have wavy axial lines in between.
The animal can be white or lightly tinted usually appearing translucent. The edge of the head shield, foot and infrapallial lobe is often of an iridescent blue/green colour.
The bullinids possess a large head shield in which the anterior corners are folded under creating a funnel to the sensory Hancock’s Organs. Posteriorly the head shield is well developed into two large lobes covering the front and sides of the shell. The eye spots are visible medially between these lobes. There is an infrapallial lobe extending posteriorly from the aperture and is usually visible behind the shell forming an exhalant siphon.
The foot is usually broader than, and extends posteriorly past, the shell. It has angular anterior corners and a broad and rounded tail.
The large gill is plicate and is usually well contained in the mantle cavity not being visible externally.
The Bullinidae feed on polychaete worms.