254 DESCRIPTION OF CHALK CORALS. 
figure 14, exhibiting three well-defined primary cavities with numerous lateral 
shoots, the whole being united, to a certain extent, by external additions. In 
other specimens, as figure 16, the plan of development was less apparent ; but the 
example delineated had two distinct surfaces of attachment, at right angles to 
each other, and the manner of growth was probably affected by them. Figure 15, + 
displays fully the general appearance of the part by which the coral was fixed, 
the interior being in all cases cavernous, as if it had been moulded on a perish- 
able body, resembling that of the root of a large fucus ; and the edges were very 
thin though fractured. The striz on the exterior were of limited occurrence 
(figs. 15, 16), and in some cases (fig. 14) they were almost invisible ; but where 
best shown, they presented either broad, slightly raised ribs with fine intermediate 
furrows, or narrow ribs with broad furrows. The amount of thickening was very 
unequal, and the addition terminated sometimes abruptly, as if the mantle had 
been lacerated (fig. 14, {) : in a specimen lent by Mr. Tennant, it exceeded in one 
place three lines. Incrusting Bryozoa and other marine animals occasionally 
appeared, but to a limited extent, indicating no lengthened exposure of the speci- 
men on which they existed. To the previous imperfect remarks on the abdomi- 
nal cavities very little can be added. The great dimensions they, in some cases, 
attained, and the diversity of size which characterized every specimen, are well 
shown in figure 14; but the lowest extremity of the largest had as limited an area 
as that of the small horn-like projections. The best-preserved margins of the 
primary cavities were very thin, proving, so far as the specimen was concerned, 
the full extent of its upward growth. Respecting the characters of a perfect 
terminal hollow no opinion could be formed, except that in the earlier stages of 
development, the depth appeared to have been very small. The lamellz greatly 
exceeded twelve (fig. 19), and they occupied the major portion of the area, being 
very near each other: sometimes they were alternately broad and narrow ; but 
no regular sequence was maintained ; their thickness also varied, and some of 
them were slightly bent or waved in the range towards the centre; their sides 
were spinous, as well as edges, so far as the latter could be ascertained ; and 
occasionally a lateral junction of the plates was perceptible. The centre appeared 
to be a simple union of the broadest lamelle. 
