The members of this family are about the size of the smaller Gulls, and combine the structure of Gannets or Cormorants with the habits and appearance of Terns. They have a satiny white plumage, with a few black markings. The bill is pointed, not hooked, the nostrils are narrowly pervious, and the palate is imperfectly desmognathous, the maxillo-palatines being separate behind, though united with the nasal septum anteriorly, and the vomer being well-developed and conspicuous. Cervical vertebras 15. Ambiens absent, femoro-caudal, semitendinosus, and accessory semitendinosus present, the last-named muscle not occurring in other Steganopodous birds. Syringeal muscles present. Members of the present family are also distinguished by laying spotted eggs.
A single genus.