This group of cerithiaceans is ill-defined and little is known of the habits or anatomy of the animals. The species reported here are included in the family more as a matter of convenience than as indicating relationships. They have in common small size (from 2 to about 7 mm in length) and a complete aperture which distinguishes them from Bittium and other members of the Cerithiidae. Differences in protoconchs may, however, belie different phylogenies.
Dialids are a major component of micromolluscan assemblages of shallow reef flats and lagoons elsewhere in the Pacific. Diala flammea (Pease, 1868b) is abundant in the lagoon at Fanning Island and at Canton Island (Kay and Switzer, 1974; Kay, 1976); at Fanning these gastropods are associated with algae such as Hypnea and Polysiphonia. Finella pupoides is a characteristic component of the sediments of the turbid lagoon at Fanning (Kay and Switzer, 1974), and Finella and Scaliola spp. are abundant in the turbid lagoon sediments at Canton (Kay, 1976). In Hawaiian waters the dialids are, with one exception, subtidal, abundant at depths of more than 3 m where they appear to replace the Cerithiidae and Rissoidae as the dominant compo¬nents of micromolluscan assemblages in deep water.