A genus of conchiferous Mollusca belonging to the family Aviculidæ. The species are not numerous, only three or four having been described. The shells are elongate, in the direction perpendicular to the hinge; they are narrow, striated, sub-equivalve, their umbones straight, earless; they are nacreous internally, and covered externally with an epidermis. The cartilage pit is large, and always produced into the cavity of the shell. They do not attach themselves to other bodies, like the Aviculæ, but remain free, or bury themselves in living sponges.