Orders: Monocyclica Inadunata, Adunata, Monocyclica Camerata, Dicyclica Inadunata, Flexibilia, Dicyclica Camerata.
Jaekel (1894) has divided the crinoids into the orders Cladocrinoidea and Pentacrinoidea, the former being the Camerata of Wachsmuth and Springer (Monocyclica Camerata, Adunata and Dicyclica Camerata of the present classification), and the latter comprising all the rest, in which the arms are either free or only loosely incorporated in the dorsal cup. In minor points there is fair agreement between the American, German and British authors.
- Monocyclica in which the dorsal cup is confined to the patina and occasional intercalated anals;: such ambulacrals or interambulacrals as enter the tegmen remain supra-tegminal and not rigidly united.
- Monocyclica with dorsal cup primitively confined to the patina and an occasional single anal; tegmen solid; portions of the proximal brachials and their ambulacrals tend to be rigidly incorporated in the theca.
- Monocyclica in which the first, and often the succeeding, orders of brachials are incorporated by interbrachials in the dorsal cup, while the corresponding ambulacrals.