246 DESCRIPTION OF CHALK CORALS. 
by the polypes, occurred in Mr. Dixon’s fine suite (figs. 9,10). Outer additions, 
as before stated, were not unfrequently wanting (figs. 1, 2,3, 4) ; and such spe- 
cimens were either beset by extraneous substances (fig. 2), or not (figs. 1, 3) ; 
but in the case (fig. 2) itis probable that the animal died some time before the coral 
was buried up by sediment, as the shell occupied a large extent of surface, and 
reached nearly to the margin of the terminal cavity. Several examples (figs. 6, 5,8) 
had an uniform layer spread over almost the whole surface, concealing more 
or less the ribs. In the first the addition was (fig. 6) coated by other bodies ; 
while in the second (fig. 5) it encrusted Bryozoa, and in the third an undetermined 
parasite. The characters of the terminal cup varied considerably: the cavity, as 
shown in figure 2, is deep, the lamellz are narrow, and the reticulated centre 
occupies a large area ; while in figures 3 a, 4a, 7a & 8 a, either the depth of the 
cavity is less, or the lamella occupy greater space, or the central structure is 
much contracted ; but if the specimens thus represented or the delineations be 
studied together and in connexion with figure 3, the deviations will be found, it is 
believed, to depend on different stages and degrees of development, or on the state 
of preservation ; the relative diameters being duly considered as affecting the di- 
mensions of the reticulated centre: moreover, if the comparison be extended to 
a suite of very many specimens, other variations will appear, but no distinctions 
to justify specific separations. The internal composition of the coral was beauti- 
fully shown in the fractured example, figure 3, especially the uniform, downward 
character of the lamellz, their structure being the same near the base as in the 
terminal cavity, without a trace of filling up ; the number as well as distribution 
of the transverse plates was likewise clearly exhibited, also the unaltered nature 
of the central reticulation. Figure 4 displays a still lower exposed interior, and 
differs not from figure 3, except that the axial portion is larger and more fully 
shown. Two of the lateral germs before mentioned are delieated of their natural 
dimensions in figs. 2&7. The slightly greater instance (fig. 7) is situated 
nearly mid-way between the extremities of the coral. The diameter of the cavity 
was rather less than a line, and that of the base about twice that measurement ; 
the height barely exceeding half a line. The exterior presented sharp ribs, with 
others intermediate but scarcely discernible ; and the base consisted of an ex- 
panded layer similar to that of mature specimens of Monocarya centralis. The 
interior of the cavity was deep, but exhibited only blunt projections or rudiments 
of lamell ; and it gave not the least indication of a central reticulation. The 
other example (fig. 2) was situated close to the margin ; it had no external ribs or 
