480 Happon—The Actiniaria of Torres Straits. 
dark-brown, and grey. Sometimes there are twenty-four dark radial bands, 
alternating with as many lighter ones; the latter are chiefly formed of larger 
tentacles of a pinkish grey colour, the former of smaller tentacles, mainly of a 
green or brown colour. 
Mesenteries.—Owing to the vertical contraction of this form when preserved in 
alcohol, and to other distortions that occur, it seems to be almost impossible to get 
satisfactory transverse sections, and this renders the study of this species parti- 
cularly difficult. 1 was not able, in the specimens I examined, to determine the 
arrangement of the mesenteries, their number is about sixty. Neither in the 
living specimens, nor in the two that were sectionised, could gonidial grooves be 
detected in the cesophagus. I was not able either to discover any directive 
mesenteries, though I cannot say positively that they are absent. The muscu- 
lature of the mesenteries is very feeble, and the retractor muscle contains a 
few scattered simple, or but very slightly branched, mesoglceal plaits. 
Sphincter Muscle.—I have been able to demonstrate the occurrence of a feeble 
diffuse sphincter muscle, the position and character of which will be best under- 
stood by a reference to Pl. xxxt1., figs. 7, 8. 
Various points in the structure of this species are indicated in PI. xxxu1., fig. 7 ; 
above the sphincter is seen the parapet, two of the complex tentacles are also 
seen; the endoderm of these and that of the under-surface of the salver-shaped 
expansion of the column contain zooxanthelle; but these are absent from the 
endoderm of the oral disk, probably on account of the great thickness of the 
mesoglea in this region. Fig. 9 is a more or less horizontal section through a 
portion of the disk, and this shows the endodermal stems of several tentacles 
piercing the thick mesogloea, and also demonstrates that several tentacles arise 
from one endoceel. 
Actinotryx mussoides (5.-K. ). 
Platyzoanthus mussoides, Saville-Kent, 1893, “ Barrier Reef,” p. 155, woodcut. 
Form—Flat, exceedingly irregular in outline; margin of oral disk crenulated ; 
tentacles exceedingly short, in most instances minutely lobate, and developed over 
the greater portion of the area of the expanded disk. 
Colowr.—Oral disk light greenish brown; tentacles reddish brown, and white 
tipped; cesophagus rose-pink. 
Dimensions. —Diameter of oral disk from 359-450 mm. 
Habitat.—Thursday Island. 
I have recast Saville-Kent’s account of this form; but this, and his outline 
sketch of the group of polyps, are too vague to determine whether this is a new 
species, or merely the foregoing species. It is almost certainly an Actinotryx. 
