304 



THE WONDERS OF GEOLOGY. 



Lect. IV. 



folds of the membrane in the cells being as obvious as in a 

 specimen obtained from the sea. 



The shells of the Rotaliae and Textilarise in the chalk, 

 also contain the desiccated soft parts of the animalcules 

 unmineralized ; and by dissolving the chalk and shells 

 in weak hydrochloric acid, and immersing the residue in a 

 transparent medium {Canada balsam), the tissues are as 

 distinctly seen as in the recent state. I shall again 

 refer to this subject when treating of the organic re- 

 mains of the cretaceous system. In this place, however, 

 I would call your attention to an ex- 

 quisite example of the preservation 

 of the soft parts of an animalcule in 

 flint. The fossil here delineated (Lign. 

 52) was discovered by my friend the 

 Rev. J. B. Reade,* a gentleman well 

 known for his accurate microscopic 

 investigations. It is evidently a coral, 

 from the cell of which a polype pro- 

 truded, when it became enveloped in 

 the fluid silex : with the exception of 

 the tentacula, which appear either to 

 have perished, or to have collapsed 

 Lign. 52. so as not to be distinguishable, the 



A CORAL-POLYPE, ill flint, n t P j.\ ' * 1 



Magnified 5^ diameters). f °rm and structure of the original are 

 admirably preserved. 

 8. Xanthidia. — The minute microscopic spherical bo- 

 dies, to which Ehrenberg has given the name of Xanthidia, 

 from the supposition of their analogy to the spores of cer- 

 tain kinds of DesmidecR^ are so abundant in the flints, that 

 I must briefly notice them in this place. These fossils 

 occur both in the chalk and flint ; and though generally 



* Hector of Stone, Bucks. 



f Desmidece, : a group of organisms of doubtful affinity ; being con- 

 sidered by some naturalists as vegetable, by others as animal structures. 



