162 J. E. Duerden — Jamaican Actiniaria : 



(H. & S.) [the type], and S. Haddoni (S.-Kent), and also D. Fuegiensis (Dana). 

 The sphincter muscle is remarkably similar in all four. 



D. tubercidata, Kwiet., should also probably be transferred to Stoichactis, but 

 not D. ambonensis, Kwiet., in which the tentacles are placed in radial groups, so 

 that more than one row communicates with a mesenterial chamber. 



Whether, as in the form I identify as D. helianthus (Ellis), a single marginal 

 cycle of exocoelic tentacles alternating with all the endoccelic radiating rows will be 

 found in other representatives of the genus remains to be seen. Until this is 

 ascertained it seems doubtful if the character should be assigned generic rank, and 

 I have therefore omitted it. 



Stoichactis helianthus (Ellis). 

 (PL xi., fig. 7; PL xiv., fig. 1.) 



Actinia helianthus, . . . Ellis, 1767, p. 436, pi. xiii., figs. 6, 7; Ellis and 



Solander, 1786, p. 6. 

 Hijdra helianthus, . . . Gmelin, 1788, p. 3869. 

 Discosoma helianthus, . . Milne-Edwards, 1857, p. 256; Duchassaing and 



Michelotti, 1866, p. 122 ; Andres, 1883, p. 493. 

 Discosoma anemone, . . . M c Murrich, 1889, p. 37, pi. i., fig. 8; pi. iii., 



figs. 15—16, pi. iv., fig. 1. 



The base is a little larger in diameter than the lower part of the column ; 

 usually it is firmly adherent to the surface of rocks, or may be buried in the sand. 

 It adapts itself to the irregularities of any object to which it is attached, and is 

 generally deeply wrinkled in consequence ; preserved examples show concentric 

 and radiating ridges and furrows. 



The column is short and salver-shaped, narrowing a little above the base, 

 and then expanding enormously in a crateriform manner, so as to completely 

 overhang and hide the basal part. Usually the column is only partly embedded 

 in sand, the overhanging distal region being free and resting on the surface. Its 

 walls are somewhat thick, but slightly transparent ; the surface is smooth, and 

 grooved in correspondence with the attachment of the mesenteries. Distally 

 vertical rows of oval green verrucse occur, but they are evidently incapable of 

 attaching foreign particles to the column. The apex of the column, corresponding 

 with each mesenterial space, is slightly rounded, but is not modified to form an 

 acrorhagus. A well-marked fossa occurs between the apex of the column and the 

 base of the outermost row of tentacles. 



The disc is greatly expanded, but remains flat, never being thrown into folds 

 as in the next species. By far the greater part of it is covered with radiating 

 tentacular rows of various lengths ; the central, naked area is smooth, and the 



