260 DESCRIPTION OF CHALK CORALS. 
within ; and close to its edge, three successive layers had been exposed by an 
accidental fracture. The main branches tapered and subdivided as they receded 
from the pit, giving off also small, lateral shoots. Their upper surface was 
round and more or less ribbed, not boldly as in the mature condition of the seg- 
ments, but irregularly and faintly as in older stems. The under side, so far as it 
could be safely ascertained, was unequally flattened, as if it had been attached to 
a rough body. 
Tab. XVIII. figures 34, 34a. 
It remains to notice a fossil represented of the natural size by figure 34. The 
surface was strongly and obliquely ribbed, resembling so far that of Avogaster 
cretacea ; but it had no circular lines or other indications of segments, nor a vestige 
of a visceral cavity. At the edge of the broader extremity, several thin concen- 
tric layers were exposed, moulded more or less regularly upon each other, and in 
conformity with the exterior ribs. The transversely fractured extremity (fig. 34 a) 
exhibited also very many thin, undulating, opaque lines, representatives ap- 
parently of other similar laminz ; but they were separated by translucent inter- 
spaces, and crossed by irregular plates, which did not extend to the very centre. 
These characters justify, it is conceived, the inference that the fossil was 
originally an incrusted coral, and from its composition it is believed to have 
consisted of layers in which calcareous and animal matter alternately prevailed. 
The total want of subdivisional lines would intimate only to the extent of the 
specimen itself, a non-segmentary composition ; and nothing absolute can be 
said respecting the absence of the abdominal cavities, except that the ribs were 
much bolder than in those portions of Awogaster cretacea in which the hollows 
had been obliterated by age. It must be further stated, that no laminated, in- 
ternal constitution similar to the one just mentioned was detected in the coral 
described in the preceding notice. That peculiarity is moreover believed to 
separate the fossil from all described incrusted corals, whether articulated or 
not; but the real characters must remain to be developed by the discovery of 
further specimens. 
Tab. XVIII. figures 35, +, 36 & 37. 
The fossil next to be considered possesses many marked distinctions. It is 
attached throughout its whole extent, and consists of circular, shallow, abdomi- 
nal cavities with about eight indentations in the side, and connected by a di- 
