Paracrinoids were originally grouped together under the Orders Varicata (recumbent arms) and Brachiata (arms free standing) by Jaekel, 1900 and essentially the same groups were elevated to the Class Paracrinoidea by Regnell, 1945. Various authors have added genera to the class but the group was ill defined until Parsley and Mintz, 1975, re-defined it, establishing two orders based on the presence or absence of thecal pores rather than free standing or recumbent arms. The nature of the basals, peristomals, geometry and position of the gonopore and hydropore, thecal asymmetry makeup of the transverse uniserial pinnulated arms and the geometry and composition of the column are also important taxobases.