POLYNESIAN PORITES. 31 
form compact convex or even hemispherical masses. The aspect of the upper surface varies 
in the different specimens, owing, apparently, to the degree of crowding of the stems; the 
ragged branching tips of the stems may be fairly distinct, or they may be so close and fused 
as to form a nearly solid mass, the tips of the branchings then appearing as narrow, very 
irregular ridges separating smooth shallow valleys, The living colony extends 3 to 4 em. deep, 
The calicles are everywhere small, about 1 mm. across, and superficial. The broad, flat 
‘walls rise into cenenchymatous swellings, especially near the tips of the stems; these swellings 
may be flat-topped, or round, or thick and conical; down the sides of the stems they diminish 
to narrow waves or ridges. The whole surface is covered with finely echinulate granules, 
which tend to conceal the smooth flat wall-flakes. The complete septal formula can be made 
out in the younger uppermost calicles, where the skeletal reticulum is thinner and the surface 
granules smaller (see Pl. I. fig. 3); here the pali form an almost complete ring round a large, 
deep, and very conspicuous fossa. On the lower parts of the stems the granules are larger, 
and cover the surface much more completely, at the same time greatly thickening the septa. 
A minute central tubercle then appears in the fossa. 
This coral, like the last, is one of those rare Porites in which the wall reticulum foams up, 
causing the surface of the coral to rise up into angular flame-like stems. It is not a little 
remarkable to find two such forms (compare that last described) occurring in the same locality 
and differing so widely from one another (for other ccenenchymatous Porites, see Table IV.). 
There are six typical specimens in the British Museum and one in the Cambridge 
Museum, and there is one other specimen, g, in the National Collection which is, I think, 
a variation. It seems possible to account for all the differences between it and the rest 
by assuming a slightly more rapid growth. This would cause (a) a greater proliferation of 
the coenenchymatous upheavals, thus making the: stock more irregular and ragged, and (d) the 
skeletal elements to have a more open filamentous reticulum, so that the stiffer skeleton of the 
typical forms, with its smooth flaky walls, and the trabecule, with their frosted tips, could not 
be developed. These are, indeed, exactly the changes we find in this single specimen (see 
PL I. fig. 5, and Pl. X. fig. 5). 
Professor Verrill’s distinctions between the forms he called “convera” and “ solida” are, 
I believe, also mainly accidental. He describes S. convexa as of a dark ash colour, and S. solida 
as greyish brown. Only one of the British Museum specimens is unbleached; it is brown at 
the tips, with a tinge of olive-green appearing at the sides. I should find it difficult to decide 
whether it is convexa or solida. 
In fig. 3 the flat wall flakes are clearly visible between the surface granules. In fig. 4 
from the lower parts of a stem, the granules are so large as to conceal the wall altogether. 
The specific name convexa was given by Professor Studer to a Porites from New Guinea 
(see P. New Guinea 1). 
a, b, c. Complete stocks from the Museum Godeffroy. Zool. Dept. 99. 3. 2. 12-13, 
d, ¢, f. Portions of stocks—/ is in spirit 
—from the ‘Challenger’ Collection. } Zool. Dept. 86. 12. 9. 309-354. 80. 11, 25, 236, 
Figs. 3 and 4 are of d. 
g. The specimen figured 5 on Pl. I. and 5 
on P]. X. from the Museum Godeffroy. Zool. Dept. 99, 3. 2. 11. 
