Species attached and projecting from soft bottoms
Bloody or Eared Ark. thick, heavy sturdy, rather oblong,
up to 6 cm in length. Beaks well elevated. Anterior end short and rounded,
posterior longer and squarish. Hinge teeth small and numerous. About 25
strong radiating ribs crossed by thread-like lines. Colour white, with
silky brown periostracum. Shallow water species, on muddy bottoms or partially
buried in turtle grass areas.