130 DESCRIPTION OF CORALS. 
lamellee occupied more space than in maturer specimens. The intertubular sub- 
stance was thin, but its surface was irregular, and it ascended to the margin of 
the cup. Its exterior was more or less studded with minute tubercles variously 
arranged. Around the margin of the specimen it thinned off generally to a very 
fine edge, in some places slightly reflected upwards ; but it did not form a con- 
tinuous layer in advance of the immature tubes. In this portion traces of a reti- 
culated structure were detected. In the development of marginal tubes a semi- 
circular projecting edge was first formed, lined by a few indistinct lamella, and 
from its base a thin lamina was subsequently expanded and traversed by lamellz. 
During this process the bounding edge was extended, and ultimately formed into 
a more or less protracted oval or oblique section of the future tube—the central 
reticulation not appearing in the middle, but under the first-developed semi-— 
circular edge. In one instance a lengthened oval was divided transversely by a 
wall into two unequal partitions ; the first, occupying the earlier-formed portion 
of the whole area, being round, and, though relatively small, regular in struc- 
ture, including a central reticulation ; while the second, composed of the larger 
and later-produced division, was semi-oval in outline as well as irregular in struc- 
ture, consisting solely of obliquely extended lamella. Other indications of a 
similar process were observed, and analogous examples are alluded to in noticing 
the mode of unfolding additional tubes in mature specimens. 
The fine specimen represented in Tab. I. fig. 2. had a central cavity through- 
out its whole extent ; but the body by which it was once occupied had clearly 
perished before the development of the coral ceased, one extremity of the hollow 
being lined internally by an overlapping extension of intertubular matter. A 
third specimen of nearly equal magnitude and similar mode of growth partly in- 
crusted small Ostree, but had also partly surrounded a perishable body. Each 
had fragments of oysters attached to the surface. Other much smaller specimens 
consisted wholly of separated branches or lobes variously united. 
The points of chief interest not obvious in figure 2. were those connected 
with the intertubular substance, and the mode of producing additional stellular 
cavities. The outer side of the tubes was separable from the surrounding 
matter, and defined, in ordinary sections, by a circular line ; but it was not com- 
posed of a continuous lamina, being intersected, more or less deeply, by vertical 
fissures, and intermediately by others bent downwards. Between the circle de- 
fining the limits of the tube and the exterior of simple lobes or branches, no 
other indications of concentric, separable, perfect surfaces were detected, though 
