260 MADREPORARIA. 
P. Amirantes 1, A thin disc, with surface smooth. 
P. Red Sea 6. The surface is raised into ccenenchymatous ridges. 
P. Red Sea 7. Probably a young stage. 
The remarkable projecting dises or tongues formed by the creeping edges of the branching 
forms, P. North-West Australia 4, and P. China Sea 10, deserve mention. In all cases the 
Bryozoa which coat the under surfaces of the discs, seem to have had something to do with 
their production.* 
C. Cluster Formation of mounds, mammille, lobes, ridges, columns, and even branching stems, 
rising irregularly from explanate surfaces. 
This combination of explanate with cluster formations is placed here because the 
explanate growth is common to them all. It represents their first stages of growth, not 
merely during « short initial period but for a considerable time, and is a feature of the ultimate 
growth-form. In these forms it is always possible for explanate outgrowths to start 
anywhere from the sides of one of the up-growths and produce a new horizontal explanate 
base for fresh cluster formation. 
These growth-forms may be divided into two :— 
a. The explanate surface continues to expand horizontally. 
b. The explanate portion of the stock hangs or creeps down round the base of the 
cluster, as the latter continues to rise and to thicken. 
a. With wide persistent explanate bases. These clusters of columns, lobes, etc., differ 
from true columnar forms in the fact that they do not rise from small initial colonies directly 
as single up-growths, but spring up in close or scattered groups from the surface of already 
expanding stocks. The expanding portion is always a part of the growth-form. 
. Fiji Islands 5, Surface rendered uneven by ccenenchymatous swellings. 
. Fiji Islands 6. A fragment only ; surface smooth, with rounded elevations. 
. Fiji Islands 17.“ Mammille and tubers.” 
. Fiji Islands 19. Crumpled into mounds. 
. P. Fiji Islands 24, Mammille. 
. Sandwich Islands 7, Tall stout ridges. 
. Gulf of California 2, “ Ridges, lobes and branches.” 
Great Barrier Reef 6. Mammille, with older clusters in next group, 0. 
Great Barrier Reef 19. Perhaps belongs to next group, 0. 
. Great Barrier Reef 26. Occurs with an older cluster, mentioned in next group, 6. 
Great Barrier Reef 27, Small stalked knobs. 
. Great Barrier Reef 28. May produce single large stalked knob. 
. North Australia 3, With ccenenchymatous spikes. 
mrt tthe 
* These Bryozoa have been submitted to Mr. Kirkpatrick ; they are all of cosmopolitan genera. 
On the China Sea specimens they appear to be Cribrilina radiata and Microporella ciliata; on the 
Australian coral, a Celleyera encrusts the under surface of the disc. 
