Havpon—The Actiniaria of Torres Straits. 471 
previously come to the conclusion, from anatomical investigations, that certain 
forms collected by me, which, from an external examination alone, would be placed 
in the genus Discosoma would have to be referred to a new genus. 
Our knowlege of this group of Actiniaria is still too slight for a satisfactory 
grouping of the species. If the genus Radianthus is to be characterised by a 
really diffuse endodermal sphincter of the type of the genus Actinia or Anemonia, 
then the species R. macrodactylus and Rk. Malu might have to be relegated to the 
genus Stoichactis. 
At present the following species may be placed in this genus :— 
R. Kuekenthali, Kwietn. ‘ Actiniaria von Ternate.” Abhandl. Senckenb. 
nat. Gresellsch, xxii. 1897, p. 332. 
R. macrodactylus (H. & S.). 
R. Malu (H. & S.). 
Radianthus macrodactylus (H. & 8.) 
Discosoma macrodactylum, . . . Hadd. and Shackl., 1893; Proc. R. D.S., vur., 
p. 120. 
(PIS OCR, figs. 1-3.) 
Form.—Salver-shaped, owing to the great expansion of the oral disk, with 
numerous large suckers, crowded into a broad zone, on the upper portion of 
column ; all the tentacles are long and very contractile, their tips are perforated ; 
the accessory tentacles are placed in well-marked linear series; mouth with two 
gonidial grooves; the disk is bare of tentacles for a distance of 25 to 50mm. 
(1-2 in.) from the mouth. 
Colour.—Column olive-brown, darker above, with pale spots on upper 
portion ; disk pinkish gray peripherally, passing into pale olive green, which 
shades into olive brown round the mouth; cesophagus delicate pink; tentacles 
dove-gray, with a yellowish sheen, which is most marked at the tip. 
Dimensions.—Diameter of disk 250-300mm. (10 to 12 in.) or more; mouth, 
25mm. x 57 mm.; tentacles 40 mm. (14 in.) or more in length. 
At first sight the corona of tlis species looks like that of a very large typical 
member of the genus Anemonia (Anthea), the coloration being very similar to 
that which may be found in some specimens of A. suleata, but the fact of several 
tentacles opening into single mesenterial chambers proves it to be a Stichodacty- 
line. On an examination of the surface of the oral disk, it is seen that one or 
two pairs of mesenteries occur between those pairs which enclose the bases of 
the tentacles, 
