Diagnosis
provided by World Register of Marine Species
Articulata with cup large, stout, thick walled. Five basals and radials. Basals contiguous. Primibrachials in most species joined laterally or connected by interradial plates. Synarthries or synostoses between primibrachials 1 and 2 and secundibrachials 1 and 2. Syzygies and cryptosyzygies common. First syzygy between secundibrachials 4 and 5. Tegmen covered with small polygonal plates. Column cylindrical, may be pentagonal proximally with nodals. Cirri absent; attachment by terminal root or encrusting disk, except in Ailsacrinus. Columnal articular facets with radiating crenulae, restricted to marginal zone in pentagonal columnals; never synarthrial or cryptosymplectial at infranodals.
