200 
its thicker margin. In the very young stages already the peripherical 
part of the costae is strongly developed whilst the central part is 
wanting. The largest specimens have a strongly developed thickened 
marginal part, in one of these (fig. 51) the margin is so strongly 
curved and thickened that it rises in some parts considerably above 
the centre of the corallum. 
Among the large material there are a great number of specimens 
in which phenomena of budding, fission or regeneration have taken 
place. In one specimen the mouth has split up into two about 
equal halves. Round the new mouths the central parts of the septa 
of each half of the corallum are more or less radially arranged. 
Two septa have fused and separate the two halves of the corallum. 
Another specimen possesses two irregular excrescences on the upper 
surface. Beside one of these excrescences two secondary mouths 
have been formed. 
In the specimen represented in fig. 50 one part of the margin 
has a kind of fold. At the base of this fold the neighbouring parts 
of the theca have fused, and the septa of each side of the fold 
have United round its margin. Glose to the beginning of the fold 
at the lower surface a small calicle is visible, probably a part of 
the upper surface that was bent down by the folding of the margin 
and afterwards more or less cut off. One of the specimens of F. 
hexagonalis described above shows a similar false bud, but in this 
specimen of F. marginata there is less positive evidence that the 
bud has developed in this way. It may also have arisen as a true 
lateral bud, developed from the living tissues of the lower surface. 
The septa of the bud-like young corallum are radiafiy arranged 
round the mouth, six of them are more prominent than the others, 
though the cyclic arrangement of all the septa is not clearly visible 
as yet. The bud is attached with a broad base to the lower surface 
of the mother-corallum. 
Probably owing to the compact structure of the corallum there 
are only a few broken and afterwards regenerated specimens in 
the collection. One specimen (fig. 22) shows the first stages of 
regeneration of one half of a broken corallum. The central parts 
are regenerated in a very regular way, completing the radial arran¬ 
gement of the septa. The septa in the new part opposite to those 
of the lower cycles in the original half-corallum are stronger than 
