244 THE MEDALS OF CREATION. - Cap. VII. 
which, the radiating reticulated structure is spread out on 
the chalk, a ; the base, with its roots, is shown at 6, 
Lien. 81. VENTRICULITES RADIATUS; 2 nat. 
Chalk ; near Lewes. 
Fig. 1.—A perfect specimen in chalk, inverted, showing the external 
reticulated surface ; the apex of the base projects in the centre. 
2.—Specimen expanded, displaying the inner surface, studded over 
with the openings of the cells or tubes. 
3.—A VENTRICULITE in chalk; the lower part inclosed in flint. 
4.—Portion of a VENTRICULITE; the stem towards the base is en- 
veloped in flint, and three radicle processes spread from it into the 
surrounding chalk at a. 
These specimens demonstrate that all the flints referred to, 
have been moulded in the cavities of cyathiform zoophytes ; 
and that their diversity of figure has arisen from the amount 
of silex that happened to permeate the organism ; if but a 
small proportion of silica in solution was present, then flints, 
like fig. 4, were produced ; if the quantity were sufficient 
to fill up a considerable part of the tissues of the original, 
fungiform flints, as Lign. 80, fig. 3, and Lign. 81, fig. 3, were 
the result. The disciform flints originated from the ex- 
