An order of the subclass Calcaronea in the class Calcarea. This order comprises a rather diverse group of calcareous sponges, and includes the families Sycettidae, Heteropiidae, Grantiidae, Amphoriscidae, and Lelapiidae. Choanocytes with apical nuclei are limited to flagellated chambers and never occur lining the general spongocoel. The family Sycettidae resembles the contrasting order Leucosoleniida in lacking the true dermal membrane or cortex possessed by the other five families. The most massive skeleton (of bundles of modified triradiate spicules) is found in the family Lelapiidae, which superficially resembles the unrelated pharetronid sponges (abundant in the Permian and Triassic periods). The canal system is never asconoid (as in Leucosoleniida), but can be either syconoid or leuconoid. Leuconoid species seem to be derived from syconoid forms. Genera include Grantia, Sycon, Sycetta, Heteropia, Amphoriscus, and Leucilla.