66 MADREPORARIA. 
and open. The septa are thin, but conspicuous and rugged. The septal formula is complete. 
The number of pali varies according as there are any on the two small secondaries composing 
the ventral triplet. A columellar tubercle, sometimes flattened, rises in the open fossa, but is 
far shorter than the tall pali. The columellar tangle seems to be sparse, and shows no special 
regularity of structure. The interseptal loculi and the spaces round the central tubercle are 
open and deep. 
Three specimens of this coral were collected and described by Mr. Gardiner. The walls 
seem everywhere to foam upwards, and it is this character which clearly gives rise to the 
development of the mammille. The vertical sections show a very strong development of 
trabecule, very wide apart, especially when forming part of the intra-calicular skeleton ; they 
seem to be slightly more compact in the walls. The horizontal elements are also very thick, 
and bear witness to the flaky texture of the walls. The specimens should be compared with 
P. Fiji Islands 24, which is also mammillate, with a similar flaky skeleton of open reticulum, 
but all on a smaller scale. 
“The colour of the living colony with the polyps expanded is a dark purple.” 
a. (See Pl. XI. fig. 2. Zool. Dept. 1904. 10. 17. 22. 
b, Zool. Dept. 1905. 1. 19. 15. 
One other specimen of this coral is in the Cambridge University Museum. 
In addition to the above are two specimens (¢ and d) which appear to belong here, both 
having essentially the same type of calicles, and all being from the same locality. 
c. This specimen (cf. Pl. V. fig. 4,) appears as if it might be a chip from a basal edge, rather 
wider than any of the three colonies above described possess, otherwise its characters are exactly 
like the edges of these forms. The calicles are smaller and more crowded, and the walls thinner, 
but they still show a tendency to throw up ccenenchymatous ridges. The intra calicular skeleton 
is of the same open character, but the skeletal elements are all smooth: the calicles being 
smaller, they are less regularly symmetrical (fig. 4). The section shows the same pronounced 
trabecular structure, but the trabecule are thinner and the spaces between them consequently 
wider, while the horizontal elements, so conspicuous in the types, are here but feebly developed. 
I am inclined, on this account, to regard the specimen as a fragment of another colony, and 
to attribute the structural differences to rapidity of growth in thickness. This would account 
for the smaller and less regular calicles, and the smoothness and filamentous character of the 
skeleton at the surface. 
c. Zool. Dept. 1904, 10. 17. 23. 
The specimen d is a free nodule, which began by encrusting a piece of dead coral. This 
latter can still be seen, with great numbers of the “edges” of the encrusting coral around it. 
The calicles are again smaller, but the type is the same, and the walls show the same woolly 
-appearance of the surging reticulum. 
d, Zool. Dept. 1904. 10. 17. 24. 
