A new theoretical morphological model is introduced to describe various shell ornament patterns of cytheroidean ostracods. A wave-source model proposed here was designed with reference to the kinematics of adductor muscles. This model depicts the ornament patterns as composite waves that are defined in terms of amplitude and frequency of wave elements. Computer models successfully mimicked most of the ornament patterns seen in the Cytheroidea. The theoretical morphospace places the multiple-bracket ornamentation as an intermediate pattern among concentric, radial, and smooth patterns. The result suggests that any observed pattern can be readily derived from a multiple-bracket one by a slight change of developmental parameters.