76 
RECORDS OF THE AUSTRALIAN MUSEUM. 
of calcium from corals, shells, etc., and deposited silica in its 
room, a portion of the calcium compound also being rearranged 
and re-precipitated.” 
With the view of showing the size obtained by a single rosette, 
Prof. Church figures three costae and intermediate furrows of an 
ordinary-sized Pecten , over which it had spread. 
The best examples of Beekite in our Collection are a very large 
Spring opora from the Siluro-Devonian Lim stone of Cave Flat, 
and a Heliolites from the Wellington Caves. In the former case 
the whole of the corallite walls are converted into a granular 
chalcedonic quartz arranged more or less in lines, where the 
surface is not occupied by the Beekite rosettes, which are usually 
contiguous to one another and touching. Each rosette consists 
of a central nucleus, surrounded by concentric rings, which seem 
to slightly imbricate at their edges. As a rule there are two or 
three rings, but any number may occur up to eight. Here and 
there, two nuclei with their rings are surrounded or enfolded in 
larger and outer rings, forming, as it were, double rosettes. The 
rings are not always continuous, but broken up into circlets of 
granules ; and the more numerous the circles are, the finer and 
closer together they become. In a few cases the rosettes appear 
to have been so rapidly developed as to have become more or less 
confluent, whereby the regularity of form is in a measure lost. 
The concentric structure extends through the whole thickness of 
the corallite walls. 
In the Heliolites two conditions are apparent. In the first, 
the entire surface of the corallum, including both autopores and 
siphonopores, is converted into a series of large rosettes, obliterat- 
ing totally the two orders of polygonal corallites. In the second 
case the autopores remain as more or less rounded openings, 
the siphonoporal (“ coenenchymal ”) surface being occupied by 
the rosettes, this being a species of Heliolites in which the 
siphonopores are largely developed. 
Two well-marked instances of Beekite silicificatioii may be cited 
for comparison. Prof. James Hall has figured* a Fenestella from 
the Upper Helderberg Formation of New York State, in which 
the whole of the polyzoarium, both interstices and dissepiments, 
is converted in this way. Another case is that of Dr. F. Toula’s 
tiguref of Spirifer striato-paradoxus , Toula, from the Carboniferous 
Limestone of Spitzbergen, in which the rosettes are in some 
respects even better marked than in our specimens. 
* Ann. Report State Geologist of New York for 1882 [1888], No. 2, 
t. xxxv. (28), f. 18. 
f Sitz. K. K. Akad. Wissensch. (Math. Nat. Cl.), Wien, LXVIII., Abth. 
1, t. 1, f. 2a. 
