PROF. P. M. DUNCAN ON SITREPTELASMA R@MERI. 169 
calice the septa unite in groups at their inner ends, and bound the 
axial fossa with a more or less dense structure (figs. 1, 12); that 
this structure is continued here and there across the fossa (fig. 15) ; 
and that the smaller septa may be very generally absent or uni- 
versally present. The usual arrangement is for the long septum to 
remain unattached to others, and the rest join their neighbours 
at the free end (figs. 13, 14). Often the septa are in groups of 
three, a central one being free and overlapped by those on either 
side. ‘The septa are rarely straight, and curve slightly here and 
there. 
Longitudinal sections indicate that the septa are made up of solid 
laminee, which increase in thickness at the inner end where junction 
occurs with other septa, and that those junction-processes, grouped 
’ around the fossa, transgress here and there on its area, and form a 
kind of false columella (figs. 1, 11, 15). 
The amount of dissepimental structure is very small and variable. 
A few small curved and short dissepiments occur between a few 
septa near the wall, and they are best seen in weathered specimens, 
stretching from septum to septum. No tabule stretch across and 
close in the corallum below entirely; and small central tabule are 
not observed in some specimens, whilst a very few exist in others 
(fig. 16). A large septum may reach a tabula and have a groove 
around it there, whilst the inner ends of all the larger septa may 
join the tabula. This is exceptional, however (fig. 14). 
The coral is usually free, and when the contrary condition is 
noticed the adhesion was by the side of the sharp base, and a cica- 
trix remains. Growth occurs in a very remarkable manner, and, 
starting when about a millimetre in length with fine, light, pretty 
regularly spaced septa (fig. 18), the coral grows in height and 
breadth. Growth in this last direction necessitates a gradual en- 
largement of the diameter of the calice and a corresponding increase 
in the costal and septal number. 
The increase takes place in four regions of the periphery. The 
vertical pair of costs, and those on the other side of the corallum, 
simply grow in height; but there is a steady increase of successive 
coste on either side of where the vertical pair join the calice, and 
also where the most oblique of the costs of the concave side join 
the longest of the coste pinnate to the vertical pair (fig. 1, at 
f & «x, also fig. 11). 
At the very base are about ten costs; but the vertical pair, which 
are very distinct, have only one septum between them; there is 
one opposite to it on the other side, and thrée others on both sides: 
These eight septa, which are rather stout, converge and unite in a 
central mass. 
The theca can hardly be said to exist, and the solid structure 
beyond the broad bases of the septa merges into costal structure, 
the whole being composed of a sclerenchyma which is fibrous- 
looking. ‘The structures which resemble epitheca are clearly mural 
in office, and are not to be distinguished from those of the theca. 
Calicular gemmation occurs in some instances. 
