152 MADREPORARIA. 
In addition to the foregoing, there are in the Hamburg Museum branching Porites of dark 
brown or blackish colour, which came from the “North Coast of Australia.” Dr. Rehberg,* 
who worked on the Hamburg collection, thought they were of the same “species” as the Fiji 
form which Dana called P. nigrescens. The temptation to class all these blackish branching 
Porites together is very great. The geographical method, however, saves us. Further, even 
if we were merely grouping into morphological species, no two have the same growth-form, 
and when we look very closely we see that the calicles are not all built on the same plan. 
There are also, as here already recorded, two different kinds of skeleton, one with the 
trabecular, and one with the horizontal, elements most developed. 
NORTH-WEST AUSTRALIA. 
146. Porites North West Australia 1. (P. Australie Occidentalis prima.) 
(PL XXIII. fig. 1.) 
[Bassett-Smith Shoal, Holothuria Bank, 9 fathoms; British Museum. ] 
Description.—The corallum appears to build up thick coral crusts by repeated thin layers. 
But the single specimen shows that, as the coral thickened, it was being destroyed below the 
living colony by boring organisms, so that its section is here thin, like that of an explanate 
stock, and there comparatively thick. Creeping edges are very thin. 
The calicles are over 1 mm. in diameter, from 0°5 to 1 mm. apart, superficial, ill-defined, 
and very inconspicuous. The walls are built of layers of flat flakes, which are covered with 
shapeless granules, twisted threads, and even scales, the granules representing the trabecule 
and the others representing the beginnings of the next layer of flakes spreading out from 
the rising trabecule. The septa are tongues of these flakes, separated by thin interseptal 
loculi, which straggle to various distances over the wall. The septa themselves become sym- 
metrical, their top edges mostly roughened by the frosted wall granules or threads running out 
along them; the ordinary septal formula can be made out, but the pali and the palic formula 
are often obscured. When seen their tips are large, and frosted, flush with the septa, and in 
formula F, sometimes also B (fig. 3, Introduction, p. 19). There seems to be no appreciable 
depth to the fossa in which a central tubercle rises, and the interseptal loculi are equally 
shallow, hence the calicles are inconspicuous. 
The section shows an equal development of trabecular and horizontal elements, the former 
appearing the more conspicuous, being straight and parallel, while those of the latter are wavy 
and irregular. The colour of the unbleached coral is the same bright yellowish or orange-brown 
characteristic of so many of the representatives of this North-West Australian group. 
* Abh, Naturw. Verein. Hamburg, xii. (1892) p. 4’. 
