INDIAN OCEAN PORITES. 225 
without radial symmetry, and like so many smooth round grains of different sizes adhering 
to the sloping walls. Fusions of septa can here and there be traced, and jagged irregular 
interseptal loculi. Pali are only occasionally hinted at. 
The section is an open loose reticulum, in which the concentric elements, though irregular, 
are more pronounced than the trabecular. The colour of the unbleached stock is a warm 
brown. 
This coral is as remarkable as the last. There is certainly no other Porites with such 
a strange irregular arrangement of septa. 
a. Zool. Dept. 82. 10. 17. 160. 
b, A detached branch, but not of a. Zool. Dept. 82. 10. 17. 157. 
The four following corals form together a remarkable group. They live on sand, and are 
all branched ; each consists of a central body, from which branches radiate ; when the branches 
are long, it may be dead or merely covered with stray patches of the living colony, which are 
then for the most part confined to the processes. The stocks rest on the tips of the branches. 
Three of these corals look alike, having the same buff colour; one is of a dull grey. Two 
are from the Marie Louise Island, and two from Providence Island. 
The grey specimen from Providence Island can easily be seen to be distinct from the 
other three; but it is difficult to resist the temptation to describe them all under one 
heading, as was done with the collection of Montipores * from these localities, which showed 
the same method of growth—in adaptation doubtless to the nature of the sea bottom. But 
the closer these Porites are studied the more clear does it become that they are different 
both in important details of growth-form and in structure of calicle. 
And here we may ask why it should be necessary to assume that they must be of the 
same species, simply because at first sight they look alike and all live within a circumscribed 
area. The probability seems to me to be all the other way. Their resemblance may be due 
to the similarity of the environment. The fact that the Montipores above referred to are 
difficult to distinguish from these Porites shows how powerful the influence of the environ- 
ment may be in impressing converging characters upon members even of different genera 
(ef. P. China Sea 4, p. 168). The similarity therefore of members of the same genus might 
be expected, and it is the differences we find in them which are of importance. I feel, 
therefore, that it is safer to describe the forms separately. 
235. Porites Amirantes (98. (P. Amirantium tertia.) 
(Pl. XXXITI. fig. 3; Pl. XXXV. fig. 26.) 
[Marie Louise Island, 17 fathoms, sand and coral, coll. H.M.S. ‘ Alert’; British Museum. ] 
Two specimens. 
Description of specimen a.—The corallum is free ; it consists of a central elongated body, 
from which constricted knobs arise, and from the tips of these again other knobs, so that the 
* See Vol. III. p. 37. 
2G 
