Desirous of pursuing the indications afforded by the circumstances above specified, I proceeded to examine many specimens of flint containing fragments of the striated shell in which the substance of the shell itself was still preserved, and in several instances observed evident traces of the siliceous globules of the cast, imbedded in their testaceous matrix; by submitting such specimens to the action of a diluted acid, that matrix was easily removed, and the casts themselves thus laid open by the destruction of their envelope, exhibited a perfect resemblance to the specimens previously described; the origin therefore which my former conjectures had induced me to attribute to those specimens now received the confirmation of a decisive experiment.
The two compartments of fig. 3, exhibit representations of a specimen of the kind last described, before and after its denudation by the action of the acid. The specimen itself from which the latter draught was made, is submitted to the Society, together with the remainder of the mass of flint from which it was broken in an unaltered state.
The succeeding figure (4.) exhibits, on a scale rather enlarged, a section carried vertically through a part of the specimen just described. The cellules forming the matrices of the globular casts will be seen in this section to have occupied nearly the whole thickness of the plate of shell. The numerous filaments extending between the globules in every direction, preserve the traces of as many minute tubes in which they must originally have been moulded, and it will be farther perceived that each globule is connected with the flinty envelope immediately above and below its centre by two thicker stems resembling the extremities of a projecting axis.
The next specimen of the suite (fig. 5.) is a large fragment of some nondescript shell of the same striated structure; on a part of
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