Diagnosis: Tentacles shield-shaped, retractor muscles absent, respiratory trees and tubefeet present. Calcareous deposits usually in the form of tables or derivatives of tables.

Remarks: Of the three families (Stichopodidae, Holothuriidae and Synallactidae) in this order, one, the Synallactidae, comprises mainly deep-water forms, while the other two are more or less restricted to shallow waters.