Bryozoan:
Like brachiopods bryozoans are abundant in Paleozoic limestones and have calcite fibers arranged generally parallel to the shell wall. The shapes of these allochems however reflect that they are colonial organisms. Circular to ovoid intraparticle pores (former living chambers), are evident in many byozoan fragments. If the pieces are broken into such small bits that you can no longer discern this larger structure, then they are difficult to discriminate from similarly comminuted brachipod fragments.