VENTRICULITES. 
101 
before mentioned, and establishes the identity of 
the chalk and flint specimens. 
A turbinated flint fills up the lower portion of the 
funnel-like cavity, and is surrounded by the im- 
pression of the external surface of the upper portion ; 
several radical processes proceed from its base. The 
dissimilarity in the size and sliapc of the hints, 
represented page 98., is jiurely accidental, arising 
from a greater proportion of silex having been 
deposited in the one instance than in the other : 
if, in this example, the quantity of silex had been 
sufficient to have filled the entire cavity, the flint 
thus formed would, in every particular, have re- 
sembled figure 1, instead of figured. No. 8. 
Among the singular forms assumed by the sili- 
ceous specimens of ventriculites, none are appa- 
rently more difficult of explanation than the broad 
annular flints occasionally found on the ploughed 
