class of Organic Impressions^ tsfc, 331 



Desirous of pursuing the indications afforded by the circum- 

 stances 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 ob- 

 served evident traces of the siliceous globules of the cast, imbedded 

 in their testaceous matrix j 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 de- 

 scribed ; the origin therefore which my former conjectures had 

 induced me to attribute to those specimens now received the con- 

 firmation 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 de- 

 scribed. 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 m.ust 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. 



Th-e next specimen of the suite (fig. 5.) is a large fragment of 

 some nondescript shell of the same striated structure ; on a part of 



2 T 2 



