These are the Alcyonaria and the Zoantharia.
There are, however, several groups of Zoantharia in which the mesenterial arrangement of the adult differs widely from that just described.
(For an account of coral formations see Coral-Reefs.) In the present state of our knowledge the Zoantharia in which a primary cycle of six couples of mesenteries is (or may be inferred to be) completed by the addition of two pairs to the eight Edwardsian mesenteries, and succeeding cycles are formed in the exocoeles of the pre-existing mesenterial cycles, may be classed in an order Actinjidea, and this may be divided into the suborders Malacactiniae, comprising the soft-bodied Actinians, such as Actinia, Sagartia, Bunodes, &c., and the Scleractiniae, comprising the corals.
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