Septifer bilocularis is a bivalve from the Mytilidae family, also known as the Box Mussel. It has a thick, elongate shell that varies in shape, of a deep green colour that gradually becomes brownish and paler towards the umbones, (the highest point of each articulating part of the shell). The interior is a bluish grey to purplish brown.
This species is present across the Indo-Pacific region, from East and South Africa to Japan, Australia, New Caledonia and Eastern Polynesia. Recorded depth range is between 0 to 15m. It is found on exposed areas such as rocky shores, coral reefs that experience strong currents. It can be found living with algal species, Corallina officinalis, in rock pools between tide marks.
The conservation status of this species has not been evaluated yet.
 ‘Septifer Bilocularis, Box Mussel’.
This species can reach a maximum length of 5cm.