146 Happon and Durrpen—Some Actiniaria from Australia and other Districts. 
Dise and Tentacles—The mesoglea of the dise is very thick, crowded with cell- 
islets and incrustations. 
(sophagus.—The ectoderm is folded, the foldings being partially accompanied 
by processes of the mesoglea. The cesophageal groove is well marked, the 
mesogloea being here a little thickened. The ectodermal muscle is feebly 
developed. In the mesoglcea are numerous cells and cell-islets. 
Mesenteries.—The whole internal structure of the polyps is very badly pre- 
served. The endoderm is wholly macerated, leaving numerous zooxanthell; no 
musculature can be distinguished. In each of the mesenteries is a large basal 
canal extending the whole vertical length, and containing numerous large yellow 
nematocysts. Various other canals or sinuses are seen in transverse sections of the 
mesenteries. 
Gonads.—No gonads present. 
Palythoa liscia, n. sp. 
(Pl wares tie. Ae) 
Form.—Contracted polyps not projecting, or but very slightly so, above 
the surface of the ceenenchyme. The upper surface of the colony is consequently 
very uniform, and the boundary between the individuals is not well marked; the 
polyps are irregularly arranged, but not crowded; each polyp has about fifteen 
capitular ridges and furrows. The colonies are very low and flat, the margins 
tending to incrust the objects upon which they grow. 
Colour.—Sandy. 
Dimensions.—Average diameter of contracted polyps at surface, 5mm.; average 
thickness of colonies, 10 mm. 
Locality —Mombassa, East Africa, collected by Dr. J. W. Gregory, of the 
British Museum. Three colonies incrusting and almost surrounding an irregular 
base of nullipores. 
The specific name has reference to the smooth appearance of a colony when in 
alcohol. 
Body-wall—The ectoderm covering the peripheral surface of the colonies has 
almost entirely disappeared. The mesogloea uniting all the polyps in the colony 
is rather thicker than in P. gregorii, but isolated cells, cell-islets, and lacune, of 
all sizes, similarly crowd the mesogleea; the islets and lacunze contain the large 
yellow nematocysts and zooxanthelle. The incrustations are of the same nature as 
those of the former species, principally coarse sand grains, but the distal portion 
of the polyps do not appear to have so many sponge spicules. The incrustations 
extend throughout the mesoglcea. 
