Part IT.—Stichodactyline and Zoanthee. 155 
and of one form; either finger-shaped, knobbed, pointed, or vesicle-like; a 
peripheral series, arranged in cycles, is usually distinguishable from an inner 
series, arranged only in radial rows; one or more rows may communicate with 
the same mesenterial space. Mesenteries very numerous, many of which are 
perfect. Sphincter muscle present or absent. 
As the Actiniaria of tropical regions are more studied, the genera embraced 
under this family become more and more numerous. In addition to the type 
genus Discosoma, the genera Radianthus, Stichodactis, and Helianthopsis, all 
erected by Kwietniewski (1898), are anatomically known; Haddon (1898) adds 
Discosomoides and Stoichactis; while in the present communication I increase 
the family by including within it the genera Actinoporus, Homostichanthus, and 
Ricordea. 
From these, and from the definition given above, it will be seen that the 
family includes a very heterogeneous assemblage of forms, corresponding in this 
respect with the Sagartide among the Actinine. The only constant feature 
appears to be that the tentacles are all of the same form in any one species, and 
cover the greater portion of the disc; but apparently in no two genera are the 
peripheral and the inner tentacles similarly related. It will probably be found 
advisable later to separate as sub-families forms in which only one row of tentacles 
communicates with a mesenterial chamber from those in which, as in Actinoporus, 
two or more rows may originate from the same mesenterial chamber. 
Following the work of M*Murrich, Simon, and Kwietniewski upon various 
forms, Professor Haddon (1898, p. 469), in his recent paper, endeavours to introduce 
some order into the group, but significantly remarks: ‘‘ This family will require 
a good deal of working at before it can be satisfactorily classified,” He does not, 
however, attach that importance to the relationships of the peripheral to the 
inner tentacles, and of both to the mesenteric chambers, from which I am hopeful 
. that much assistance can be obtained in arranging the numerous members of the 
family. 
Genus.—RICORDEA, Duchassaing and Michelotti. 
Ricordea, - » . Duchassaing and Michelotti, 1860; M*Murrich, 1896; 
Haddon, 1898. 
Heteranthus, . . . (Klunzinger, 1877), M*Murrich, 1889. 
Discosomidee, in which the marginal tentacles are small, dicyclic, finger-shaped 
or slightly knobbed; inner tentacles a little smaller, of the same form, in single 
radial rows. Sphincter muscle absent. No gonidial grooves. An ectodermal! 
longitudinal muscular layer on the column-wall, and on the stomodeal wall. 
Numerous perfect mesenteries ; mesenterial filaments devoid of ciliated streak. 
