20 MADREPORARIA. 
the level of the rest of the ring. Other cases in which pali are not developed are when the 
trabecular elements are greatly degenerated either in favour of the horizontal elements, or when 
they have melted down into a streaming lamellate reticulum ; for the rod-like character of the 
trabeculz, on which the formation of the pali depends, is then lost. 
Lastly, we may again refer to the loss of all the pali so commonly seen in deep calicles, 
and to the correlation which seems to exist between the development of the pali and the depth 
of the calicle; the deeper the calicle, the less developed the pali; and the shallower the 
cealicle, the more developed the pali. This distinction has already been referred to as having 
had much to do with the founding of the genera Synarea, p. 9, and Neoporites, p.10. The fact, 
however, just pointed out, that the appearance of pali is mainly a question of the development 
of rod-like trabecule in height, shows that this difference is due to a growth variation of certain 
parts of the skeleton, without any fundamental change of plan. For instance, when the 
trabecular elements are undeveloped, as compared with the horizontal elements (see Pl. XX VI. 
figs. 1, 2), or, again, when the trabecule are long, thin, twisted lamelle, there may be but 
very slight traces of pali. Hence their absence from so many deep calicles may be simply 
explained by regarding the calicle as deep because the vertical elements lag behind, and the 
trabecule of the septal granules and the pali have not developed as high as the wall trabecule. 
This tends to confirm our argument that the circle of short, free septa, shown in A, fig, 3, is not 
an original condition, for if we take A, -b, fig. 2, and imagine the septal trabecule repre- 
senting granules and pali left out, we should get a deep, open pit with vertical rows of spikes 
projecting from the walls, and representing the radial junctions which would have joined the 
wall trabeculee with the septal trabeculee had the latter been developed. 
When the septa tend to be lamellate, the pali may have the V-shape which has been 
noted as occasionally occurring in G'oniopora. 
This explanation of the case throws light upon another rather puzzling phenomenon. Not 
seldom it may be noticed that septal granules seem to take part in the formation of the palic 
ring; this may, apparently, be the case with either of the directive septa, or with the two 
ventral secondaries. We now see that this would be accounted for if any of these septa were 
very short, and stopped at the trabecule of the septal granules. This relationship between the 
palic formula and the ring of septal granules is only indicated on Diagram E, although it 
probably holds in many other cases where the formula is complete (see e.g. P. Ellice Islands 9). 
The two small pali on the ventral secondaries probably frequently belong to the ring of septal 
granules. 
This is one of the cases above hinted at, in which the results of this final analysis carry 
our insight somewhat deeper into the morphology than was the case when the systematic 
descriptions were written. The diagrams were drawn from the specimens before any correlation 
between the pali and the septal granules had been detected. 
The Columellar Tangle-—This structure obviously depends upon the appearance of con- 
centric synapticule in the ccutral region of the calicle. A glance at B, fig. 2, shows 
synapticule starting or fully developed between the septal granules (or trabecule) and between 
