Rotaliotina discoidea , common name the discoid delphinula, is a species of small sea snail, a marine gastropod mollusk, in the family Liotiidae.
The size of the shell varies between 4 mm and 9 mm. The shell has a discoidal shape, with a flattened spire. The periphery shows two prominent ribs, connected by lattices which a subspinously project. The surface contains clathrate ridges, the interstices of which are finely striated.
This marine species occurs off the Philippines, Papua New Guinea and Australia (Queensland) and Norfolk Island and Lord Howe Island.