60 MADREPORARIA. 
The calicles are small, uniformly 1 mm. in diameter, sub-circular, and deep. The walls, 
though not thick, are a close, flaky reticulum, mostly with a slight denticulate median ridge, 
the component denticles or trabecule being tall and thick. The septa begin to project some 
way below the top of the ridge, and almost always form the typical septal formula; the free 
secondaries (see, without reference to septal granules, E, fig. 3) on each side of the ventral 
directive are quite short, as is also the dorsal directive. The pali, seen from above, are not 
conspicuous, but seen laterally, rise as stout, tapering rods. The fossa is deep and circular, 
without columellar tubercle. The interseptal loculi are round and open. 
This Porites differs mainly in the character of its walls from P. Fiji Islands 20; the septa 
are exactly alike; they are in both very short, and the pairs which fuse enclose an angle of 
nearly 60°. ; 
The Red Sea form, called by Milne-Edwards “alveolata,”’ is, as I gather from my notes 
made in the Paris Museum, very different from this (see below, in the section dealing with 
Red Sea Porites. 
a. Zool, Dept. 1905. 1. 19. 10. 
37. Porites Fiji Islands (9922, (P. Fidjiensis secunda et vicesima.) (PI. IV. figs. 7, 8; 
and Diagram, fig. 8, Pl. XIII.) 
{Rotumah, coll. J. S. Gardiner; British Museum.] 
Syn. Porites tenuis Gardiner (? Verrill), Proc. Zool. Soc. (1898) p. 276. 
Description.—The corallum forms flat-topped cakes some 4-5 cm. thick. The edges of the 
cake, which project laterally some 4-5 cm. above the substratum, are thick and rounded. The 
top surface is slightly wavy; the under surface of the projecting edges is quite smooth. 
The calicles are everywhere flush with the surface, except on the outermost zone of the 
projecting edges, where growth is apparently most rapid; here (Pl. IV. fig. 7) the thin walls 
rise as ragged, incomplete membranes a little above the surface. Seen from above, the 
calicles of the uppermost surface appear as polygonal areas, uniformly 1 mm. across and 
separated by very thin ragged or frosted lines, which, under the microscope, are seen to be the 
low median ridges of reticular walls. This reticulum is fairly uniformly composed of this 
median ridge with a single ring of synapticule, which tend to expand into flakes, making 
shelves on each side of it. The septa are prominent. The pali, in formula B, fig. 3, as 
fine frosted granules inconspicuous to the naked eye, rise to the level of the top of the wall- 
ridge; the two smaller granules on the free ventral secondaries appear to be parts of an 
outer ring of septal granules (see E, fig. 3). The small columellar tubercle rises nearly as 
high as the pali, and rests on conspicuous radiating strands without formation of a visible 
columellar ring. 
On the under surface the frosted pali and wall-granules gradually enlarge to form 
ultimately a frosted mosaic, in which the calicles become less and less recognisable 
(PI MIVete ss): 
