212 
in which the septa have a slightly more solid structure. Excepting 
these differences the type-specimen of F. sibogae in every respect 
closely agrees with the specimens of F. moluccensis from the Leyden 
Museum and those of my material. In my opinion F. sibogae may 
hardly constitute a definite species, in all probability it is an 
aberrant form of F. moluccensis^ perhaps a local variety. This latter 
species is very variable: the specimens in my material also show 
considerable differences in the size and number of the costal spines. 
One specimen in my collection (fig. 49) which very probably 
belongs to F. moluccensis, also has some likeness to certain specimens 
of F. cyclolites. The structure of its upper surface closely resembles 
that of F. cyclolites, the lower surface is quite similar to that of 
some specimens of F. moluccensis: the chief costae are beset with 
numerous irregular spines. This specimen shows some abnormalities 
owing to the faet that the living tissue of the mouth and the 
neighbouring parts had been destroyed. At the central part of 
the upper surface next to the old axial fossa a number of small 
secondary mouths have developed, Between some of these and 
the old axial fossa a kind of ridge has been formed on which the 
new-formed septa belonging to the secondary mouths have arisen. 
In the central part of the lower surface of this specimen also the 
living tissues had vanished, which stimulated the neighbouring 
parts to augmented growth and this has resulted in the formation 
of a stalked bud of somewhat irregular shape (fig. 49). 
In F. moluccensis at the central elevation of the upper surface 
of the corallum often secondary calicles are formed. In fig. 75 some 
young stages of these secondary mouths are represented. Only a 
few septa are interrupted at the place where the new mouth has 
developed and the parts of these septa nearest to the secondary 
mouth have grown out in a radial direction towards the centre of 
the little calicle. Also new septa have been formed as excrescences 
from the uninterrupted septa nearest to the young mouth. The 
axial fossa of this specimen shows no irregularities. Fig. 76 shows 
a further stage of formation of secondary calicles. On every side 
of the central elevation of the oral surface there are a large 
number of secondary calicles (on the whole about 38). The old septa 
of the mother-corallum are often divided into three or more 
parts. Here the secondary mouths are mueh larger than in the 
