CLASSIFICATION OF ACTINIARIA 295 



Megalactis, Ehr., 1834. 



Actinodendridae with the arms longer than in Actinodendron, 

 the oral faces of the arms freer from tentacles, the ultimate branches of 

 the tentacles simple and pointed, not bifid. (See Part II, Text-fig. 14, K.)- 

 Species : 

 M. griffithsii, Saville Kent, 1893, pp. 35, 147. (See Haddon, 

 1898, p. 493.) 

 And probably at least one other. 



I have followed Haddon and Saville Kent in keeping 

 Megalactis separate from Actinodendron, as I think 

 it should lie, although not yet well known. 



Family 13. Thalassianthidae. 



Thalassianthidae, McM., as used by Haddon, 1898, p. 482, 

 and Carlgren, 1900, p. 86. 



Endomyaria with definite base. Body with or without verrucae 

 above. Disc circular or waved or puckered. Not more than one den- 

 dritic tentacle to each exocoel — exocoelic tentacles all dendritic. Several 

 simple or dendritic tentacles and several (sometimes many) modified 

 tentacles or nematospheres on many of the endocoels, these sometimes 

 gathered up on to a definite permanent elevation or even finger-like 

 lobe of the disc (the nematospheres being aboral), which may cover an 

 endocoel and the two adjacent exocoels. Sphincter of variable develop- 

 ment, from more diffuse to more circumscribed, not very strong. Mesen- 

 terial musculature well developed, but not unusually strong, retractors 

 more or less diffuse. Numerous perfect mesenteries. 



Genera : T h a 1 a s s i a n t h u s , C r y p t o d e n d r o n , 



A c t i n e r i a . 



Thalassianthus, Leuck., 1828. 

 Heterodactyla. Ehr., 1834. 



Thalassianthidae with verrucae above, which may be in rows, or with 

 none, and they may vary in distinctness. Margin may be distinct or 

 notched. Disc may be folded or puckered up, or not. Marginal tentacles 

 dendritic, without nematospheres, not more than one per exocoel. The 

 endocoelic tentacles are also dendritic, but many of them arranged on 

 elevations or permanent lobes of the disc, and occupying the more oral 

 part of the elevation, which typically possesses aboi'ally a bunch of grape - 

 like stinging batteries or nematospheres (see Part II, Text-fig. 14, e). 

 Siphonoglyphea two or several, directives present in the first case, 

 NO. 262 y 



