AUSTRALIAN PORITES. 127 
The smooth rounded summit is not in the centre, but on one side. One slope is con- 
sequently very steep, and even slightly overhanging ; while the opposite side slopes at an angle 
of 45°. The growth-form may, in fact, be illustrated by fig. 19 on Pl. XIII. The symmetry 
of the crisp intra-calicular skeleton makes this a beautiful specimen. 
a. Zool. Dept. 92. 12. 1. 334. 
116. Porites Great Barrier Reef (42,23, (P. Queenslandice tertia et vicesima.) (Pl. XVI. fig. 4. ; 
Pl. XXI. fig. 13.) 
[Thursday Island, coll. W. Saville-Kent; British Museum. ] 
Description.—The corallum is massive, and with surface raised sharply into rounded 
eminences and ridges, with convex depressions or valleys. The edges are closely adherent, and 
bend under. 
The calicles are large, 1:5 mm. and under, nearly superficial and conspicuously polygonal. 
The wall is a raised, but low, membranous ridge or plate, with nearly smooth edges. Within 
it and slightly below it is a smooth, continuous flaky shelf separated from the wall ridge by a 
ring of pores. This shelf can be traced to the septal synapticule, and from it rise nearly 
symmetrically the twelve septal granules, often T-shaped, and only here and there running 
backwards to join the wall-ridge. From the septal granules very thin, straight septal plates 
run to join the pali, which rise as high as the wall as a conspicuous ring. - The formula is 
that shown in ©, fig. 3. The principals are large frosted granules. The dorsal directive is 
often a plate. 
On the higher parts of the stock the fossa is deep, and the central tubercle sometimes 
absent. All the characters become more pronounced down the sides. 
The section shows developed trabeculz separated by large round pores, and joined by stout 
horizontal pieces. The colour of the unbleached stock is sepia. 
There are two large fragments which may have been broken from one stock. On the 
upper part of the stock, according as the central tubercle is absent or not, we have the appear- 
ance of a dimorphism, some fosse showing to the naked eye as deep pin-holes. 
The Porites which comes nearest to this is that deseribed below—P. Great Barrier Reef 30. 
It is probably a variety. 
a, b. Zool. Dept. 92. 12. 1. 349 and 324. 
117. Porites Great Barrier Reef 4924. (P. Queenslandie quarta et vicesima.) 
(PE SOV fig: 5; Pl. XXT fig: 14.) 
[Thursday Island, coll. W. Saville-Kent; British Museum. | 
Description —The corallum rises originally from an explanate base, whose sharp edges may 
droop or project a little beyond the base of support. It consists of a continually thickening cluster 
