126 MADREPORARIA. 
The walls are broad, and flat-topped round the edges and on the higher parts of the surface. 
They consist of a very delicate and elegant filamentous reticulum, beset with small blunt 
points like a filigree; into this the interseptal loculi are gashed back, so that their shapes are 
almost petaloid; threads of the filigree may sometimes form a zigzag border. In the depres- 
sions the calicles are minute, and the walls reduced to single zigzag lines, often incomplete. 
The septa show the same blunt points on their sides and edges, making them look crisp 
and irregular. They are often incomplete, the ventral triplet being then reduced to a single 
directive. Those which are developed are long, with septal granules like portions of the wall, 
and pali like small inconspicuous stars with blunt rays. The ring of paliis small, and their 
number varies from four to six, according as the directives carry pali or not. The columellar 
tubercle and tangle are deep down and obscured. 
The vertical section is delicately and elegantly trabecular. The colour of the unbleached 
stock is light yellowish brown. 
This elegant little form is unlike any other known explanate Porites, 
a. An unbleached stock, nearly complete. With this are 
b, a bleached fragment of the same, broken from the } Zool. Dept. 1904. 10. 17. 40. 
edge, and c, a younger complete stock, 3 by 1°5 cm. 
115. Porites Great Barrier Reef (4222. (P. Queenslandice secunda et vicesima.) 
(GOE DOs, Ba Jal O06 aie Ill) 
[Thursday Island, coll. W. Saville-Kent; British Museum. ] 
Description.—The corallum rises into a mound with smooth surface and sloping sides, the 
closely encrusting edges spreading gradually over the substratum, but without any flat basal 
expansion. The height attained is about 3 cm. for a basal diameter of 5 cm. 
The calicles are conspicuous because of the deep central fossa, about 1 mm. in diameter, 
but varying in size owing to the numbers of intra-calicular buds, The walls are thick, and 
tend to be built symmetrically—that is, on each side of the primitive wall, which forms a 
nearly straight median thread-like ridge, crisp, frosted, or echinulated, the septa are joined by 
stout synapticule, which form inner walls. These then make the walls thick and reticular. 
The septa, with finely echinulate but much interrupted edges, slope rather steeply down 
towards the small deep central fossa, which is surrounded by two rings of very small echinu- 
late granules, the smaller and more irregular being the septal granules, the larger, the pali. 
The last-named are usually in the complete formula of eight, but only the four principals show 
any signs of special development ; the rest are not thicker than the rest of the septa. There 
is no visible central tubercle, and the columellar tangle is deep down and obscured. 
The colour of the unbleached coral is rich red-brown. 
This is another Porites in which the fossa is deep and open, and the pali feebly developed. 
It grew slightly asymmetrically on a flat stone. 
