36 MADREPORARIA. 
slope only gradually round a much smaller fossa, with larger granules in its base. There is 
no regular system of pali; the septa, though approaching one another as if about to fuse, 
rarely actually meet. 
The interseptal loculi run right up to the wall-ridge, and give the calicles a stellate 
appearance. 
There is only one specimen of this coral. Its growth-form is not very clear, but its 
calicles should enable it to be identified again without difficulty. 
The figure shows the largest lateral calicles. In the centre of the figure is a patch 
showing the skeletal elements abnormally thickened. 
a. Zool. Dept. 1904. 10. 17. 3. 
9. Porites Tonga Islands qo4, (P. Tongaensis quarta.) (Pl. I. fig. 9; Pl. XIIL fig. 4.) 
[Tongatabu, coll. J. J. Lister; British Museum.] 
Description.—The corallum forms pear-shaped knobs round the tips of branching corals; 
the surface is wavy, and the edges creep downwards, closely adherent. 
The calicles are small, averaging 1 mm., but conspicuous and angular. The walls are 
very thin and membranous, consisting of flattened trabecule arranged in an irregular zigzag 
round the calicle ; their upper edges may be either denticulate or straight with a few incisions. 
The septa, which are extremely thin, are indicated round the margin as blunt points at the 
angles of the zigzag ; they project lower down as twelve thin plates, very perforate and inter- 
rupted and fusing irregularly, and sometimes suggesting fig. 3, E. The pali rise as small frosted 
or angular granules. On the tops of the waves of the surface, where the calicles are largest, 
the walls are thickened a short way below the ridge by a ring of synapticule, and at the 
points where they join, the septal granules may rise to form a ring round the pali. The fossa 
is a deep, round pinhole, with rarely any trace of skeletal tissue visible from above. 
This coral is represented by only one specimen. Its method of growth and its calicles 
should be easily identified again. 
Its affinities with the three following forms can only be made out when we have a much 
greater series for examination. 
The young buds, which are plentiful on the uppermost surface, rise up like small, gaping 
membranous rings. Double calicles are numerous. The living layer extends 6 cm. and more 
round the stalk-like base. 
The fig. 9 is from near the top of the stock; it shows also a few cases in which the walls 
are thickened. 
Compare observations on this growth-form under P. Tonga Islands 7. 
= Zool. Dept. 91. 3. 6. 82. 
