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Genus Phymactis Milne-Edwards 1857 p. 274
Actiniidae with well-developed basal disc. Column covered thickly with vesicles, simple or more or less compound, and sometimes fused inseparably with each other. Margin distinct, with well-developed fosse. Marginal spherules present containing, in comparison with other Actiniidae, rather few atrichs but very numerous and very long basitrichs and numerous spirocysts. Sphincter decidedly diffuse. Tentacles short, usually hexamerously arranged, their longitudinal muscles ectodermal. Radial muscles of oral disc partly mesogloeal. Two to several siphonoglyphs which need not correspond to directives. Numerous perfect mesenteries, at least the two oldest cycles fertile. Parietobasilar and basilar muscles well-developed. Cnidom: spirocysts, atrichs, basitrichs and microbasic p-mastigophors.