40 
Bulletm of Natural History Society. 
A peculiarity of the calcareous column is that it is usually 
surrounded by a casing of more silicious matter. A space 
of a quarter of an inch, or more, may separate two of the 
Problematical fossil from Laurentian limestone at St, John, N, B. 
Side view of a portion of a column. Reduced ^ diam.* 
columns, the space between being filled up with an irregular 
and broken calcareous deposit. 
The microscopic characters of these columns and their 
layers have not been studied, but to the naked eye the more 
silicious layers, when well preserved, are distinctly beaded 
as if they were the filled up chambers of an organism, in which 
the chambers were imperfectly separated from each other. 
A peculiarity of this object is that of the sudden cessation 
of growth, either of part, or of the whole of an individual 
column. In a case of this kind the space thus left vacant, 
is occupied by the extension over it of the layers of a neigh- 
boring column or by the growth of one or more new indivi- 
duals on the senile surface. 
These new columns have in all cases a dome-shaped or 
hemispherical form, which they retain till they are as large 
or larger than a finger-end ; after which the layers begin to 
* From a photograph by J. S. Climo. 
