Hapvpon—The Actiniaria of Torres Straits. 497 
grey on aboral aspect, and greenish yellow on oral surface, with a pink line down 
the centre (orally); appendages nearly white. 
(B).—Column greenish grey, paler below; disk green, with dark spots (? low 
tubercles) ; tentacles, aboral aspect slaty grey, oral aspect with a pinkish central 
line ; appendages greenish. 
(c).—Column dull reddish buff below, passing into dull slaty green above, pale 
buff, with dirty white spots; disk not visible; tentacles slaty grey aborally ; 
magenta streak on oral aspect ; branches deep green. 
Dimensions.—Height, 250-500 mm. (10—20 inches); diameter of corona, 
500-750 mm. (20-30 inches) or more. 
Habitat.—Surface of fringing reef, Mer; Barrier Reef (S.-K.). 
“The variations of colour to which this species is subject are numerous. In 
one of the commonest varieties the disk and tentacles are various shades of olive- 
green, the shafts of the tentacles being the darkest. In a second variety the 
shafts of the tentacles are alone green, their pinnules and all portions of the disk 
being a pinkish brown. In a third variety the prevailing ground colours of the 
disk and tentacles are shades of light greenish grey ; some of the latter being also 
erimson-tipped. A crimson line runs on the central shaft of each tentacle and the 
pinnules in this variety, while usually pale green, are in some examples nearly 
white” (Saville-Kent). 
The twenty-four pairs of perfect mesenteries are fertile, and have a strongly 
developed retractor muscle. The diffuse endodermal sphincter is very feebly 
developed (Pl. xxx1., fig. 9), but there is no doubt as to its existence. The endo- 
derm is crowded with Zooxanthelle. 
THELACEROS, Mitch. 
Phymanthidz, with a smooth column and no sphincter muscle. 
P. Chalmers Mitchell (Quart. Journ. Micr. Sci. xxx., 1890, p. 551) described a 
new Actiniarian from Celebes, which he named Thelaceros rhizophorae, and which 
he regarded as the type of a new family, the Thelaceride. Were it not that 
Chalmers Mitchell states clearly ‘the column was quite smooth—there were no 
warts, knobs, or ridges, and there were no cinclides; there were no marginal 
spheres”—I should place this form under the older genus Phymanthus; the 
species has many resemblances to P. muscosus. 
TRANS. ROY. DUB. SOC., N.S. VOL. VI., PART XVI. 4C¢ 
