Part II. — Stichodactylince and Zoanthece. 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 ti'ojDical regions are more studied, the genera embraced 

 under this family become more and more numerous. In addition to the t}pe 

 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 tlie definition given above, it will be seen that the 

 family includes a very heterogeneous assemblage of forms, corresponding in this 

 respect with the Sagartidse among the Actininse. The only constant feature 

 appears to be that the tentacles are all of the same form in any one sj^ecies, 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. 

 Hetermthus, . . . (Klunzinger, 1877), M'^Mim-ich, 1889. 



Discosomidse, 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 stomodseal wall. 

 Numerous perfect mesenteries ; mesenterial filaments devoid of ciliated streak. 



