62 MADREPORARIA. 
39. Porites Fiji Islands 424, (P. Fidjiensis quarta et vicesima.) (PI. V. fig. 1.; 
JAG CUE, sie 118})y 
[Rotumah, 3 fathoms, coll. J. S. Gardiner; British Museum. | 
Syn. Porites exilis (partim) Gardiner, Proc. Zool. Soc. (1898) p. 275, pl. xxiv. figs. 1, 8. 
Description.—The corallum has a. thin encrusting base with thin edges (1 mm.). The 
centre thickens, and its surface rises into small mounds; as the growth-periods succeed one 
another, the centre rises as an irregular cluster of mammillations some 6 mm. thick and 10 mm. 
high, but fusing to form thicker compound mammille. 
The calicles are about 1 mm. in diameter, very shallow and sub-circular. The walls are low 
and thick for the size of the calicles; under the microscope they consist of a light elegant 
reticulum of smooth, horizontal or gently sloping flakes attached to trabecule, which may 
either be invisible at the surface or rise above the flakes and swell into frosted knobs ; the flakes 
are perforated by neat round holes, and their edges are cut out into elegant curves, with inter- 
vening tongues which run out as the beginnings of septa; one or two may even extend far 
enough to carry pali. The majority of the septa come from a lower level. The developed 
septum is not especially flaky, and the interseptal loculi are large. The pali have no fixed 
formula, but show several different arrangements ; they are everywhere conspicuous as an open 
ring of separate granules round a central tubercle, which is large and rises to the height of the 
septa. A columellar ring is generally conspicuous, and the tubercle often rises from thick radial 
spokes meeting in its base. The vertical section is open and distinctly trabecular, with great 
numbers of tabule. 
Mr. Gardiner may have been right in grouping this Fijian form with specimen a of P. Ellice 
Islands 1 as specimens of one and the same “ species,” for in habit they are all closely alike, but 
there are differences which, in the total absence of evidence, may for all we know characterise 
the representatives of the different localities, For instance, in this Fijian coral the centre is not 
only thickened, but raised into a cluster of mammille from which the expanding base slopes 
away all round. This is a very different growth-form from that of the Funafuti specimens. 
Too much stress, of course, cannot be laid upon growth-form ; great differences in it may be due 
to very trifling differences in the calicle skeleton. For example, in this very case the calicles 
are characterised by the growth of the trabecule in height; this naturally raises and lightens 
the flaky reticulum, and may well give the impulse to the formation of the mammillz, whereas 
the short trabecule of the Funafuti specimens would leave the stock thin, flat, and encrusting. 
A much longer series of specimens can alone decide the question of the true affinities. 
Mr. Gardiner’s fig. 8 is probably taken from this specimen, for the columellar ring is a 
much more conspicuous object here than it is in the Funafuti specimens of his P. ezilis, although 
the difference is not brought out in the collotype reproductions (cf. Pl. V. figs. 1, 2). 
There is an unlabelled fragment with calicles exactly like the above. It has the thick 
central region with the same trabecular structure ; the white chalky character of the epitheca is 
also the same. In Mr. Gardiner’s text he implies that only the mammillate specimen came from 
