278 MADREPORARIA, 
P. Singapore 6. The wall, showing a tendency to have an inner shelf, surrounds 
a clear ring of small septal granules, within which are large compact pali. 
*P. Ceylon 4. With walls variable ; two distinct inner rings. 
*P. Ceylon 5 differs from 4 in smallness of calicles and extreme tenuity of septa. 
P. Ceylon 7 and § differ from 4 only in characters of the skeletal elements. 
*P. Amirantes +. With complete rings of septal and palic trabeculz, with walls 
frequently reticular. 
P. Providence Islands 1. The walls mostly thicker and coarser than those of 
P. Amirantes 3 (see last entry). 
P. Red Sea 2. With wall raised, convex, reticular, and of varying thickness. 
b, iti. With one single ring distinct within the calicle, viz., the pali; the extra, wall, and 
septal trabecule, as far as they can be made out, together form the compound wall. 
*P. Society Islands 1, Wall appears at times to consist of 3 rings of trabecule. 
P. Solomon Islands 1, Wall appears to consist of three rings of trabecule. 
P. Solomon Islands 2. Septal trabecule either quite involved in, or serrating 
the inner margin of, the walls. 
*P. Caroline Islands 4. Wall a close reticulum but of variable thickness. 
P. Great Barrier Reef 1. Convex reticular walls, with septal trabecule serrat- 
ing the margin. 
P. Great Barrier Reef 27. Broad, flaky walls, with septal trabeculae sometimes 
free. 
*P. Great Barrier Reef 28 and 29. Walls proliferate into foaming filamentous 
reticulum with septal trabecul serrating inner margin. 
*P. Great Barrier Reef 32 and 39. The septal trabecul here and there free. 
P. North-West Australia 7. Septal granules irregularly involved in thick 
convex reticular walls. 
P. Singapore 3. Thick, slightly convex, reticular walls, septal granules some- 
times free and sometimes involved. 
Other cases in which extra trabecul appear in the wall are given below in Division E, 0. 
In the following it is doubtful how far the extra trabecule are normal. 
P. Ellice Islands 15 and P. North-East Australia 2 are very small convex masses with 
gaping calicles, and may be merely young stages. 
Other doubtful forms may be mentioned, P. China Sea 7, P. Ellice Islands 3, in both of 
which the trabecular arrangement is difficult to make out. 
C. Those in which there are typically no extra trabecule, but the “wall” trabecule 
(w of the diagrams) form the middle line between adjacent calicles. 
The following are the chief sub-divisions :— 
a. These “wall” trabecul are the only constituents of the thin walls, and the other two 
rings, septal and palic, are free and distinct within the calicle. 
b. The septal trabecule may be variously associated with the wall trabecule. 
i. Forming an inner ring or shelf. (Gardiner’s “Trimurate” condition, see 
Introduction, p. 16.) 
