xiv ZOANTHARIA ANTIPATHIDEA 407 



with the Madreporaria. They are solitary turbinate corals, with 

 numerous septa exhibiting a distinct bilateral symmetry in 

 arrangement. Zaphrentis, Lophopliyllum. 



Order V. Antipathidea = Antipatharia. 



The members of this order can readily be distinguished from 

 all other Zoantharia by the presence of a horny axial skeleton 

 (sclerobase) and the absence of any spicules of calcium carbonate. 

 The skeleton is covered by a thin bark which consists of a number 

 of simple, naked zooids united at their edges. The zooids bear six 

 tentacles, or if there are more than six, six large prominent 

 tentacles. In most genera there are but ten mesenteries, in 

 others twelve. In Cladopathes only six mesenteries are found. 

 The skeleton of the Antipathidea is simple in Stichopathes and 

 Cirripathes, but in all other genera it is ramified. The ramifica- 

 tion is usually profuse and irregular. The horny substance of 

 which it is composed is free from any deposit or infiltration 

 of lime. The surface of the younger branches is beset with 

 numerous short spines, the number and arrangement of which are 

 characters largely used in the determination of species. The basal 

 parts of the main axis and the thicker branches are frequently 

 bare, the zooids having died and become disintegrated. In these 

 cases the spines wear away and the skeleton appears to be smooth. 

 The presence of spines on some of the branches is, however, 

 generally sufficient to enable the naturalist to distinguish a dried 

 Antipathid from the axis of a Gorgonid, with which alone it 

 might be confounded. 



There are six complete mesenteries in each zooid, but as they 

 bear no retractor muscles it is not certain that they represent the 

 first six protocnemes of other Zoantharia. In a great many 

 species the zooids are oval in shape, the longer diameter being 

 parallel with the axis of the branch. The mouth and stomodaeum 

 are compressed and at right angles to this diameter. It is usually 

 assumed that the mesenteries attached to the angles of the stomo- 

 daeum are the directives, and that the remaining pair, which is 

 axial in direction, corresponds with the first pair of protocnemes. 

 The axial pair of mesenteries is frequently very well developed 

 and alone bears the gonads. When other mesenteries are formed 

 they always arise in bilateral pairs between the axial mesenteries 



