PART I. CHAPTER III. 



41 



Microscopic Fossils Infusoria in Flints. 



in Saxony, the species of infusoria are freshwater ; but in other 

 countries, as in the tripoli of the Isle of France, they are of ma- 

 rine species, and they all belong to formations of the tertiary 

 period, which will be spoken of hereafter. (See Part IT.) 



A well-known substance, called bog-iron ore, often met with 

 in peat mosses, has also been shown by Ehrenberg to consist of 

 innumerable articulated threads, of a yellow ochre colour, com- 

 posed partly of flint and partly of oxide of iron. These threads 

 are the cases of a minute animalcule, called Gaillonella ferru- 

 ginea (Fig. 16.) 



It is clear that much time must have been required for the 

 accumulation of strata to which countless generations of infuso- 

 ria have contributed their shells ; and these discoveries lead us 

 naturally to suspect that other deposits, of which the materials 

 have usually been supposed to be inorganic, may in reality have 

 been derived from microscopic organic bodies. That this is the 

 case with the white chalk, has often been imagined, this rock 

 having been observed to abound in a variety of marine fossils, 

 such as shells, echini, corals, sponges, Crustacea, and fishes. 

 Mr. Lonsdale, on examining lately, in the museum of the Geo- 

 logical Society of London, portions of white chalk from different 

 parts of England, found, on carefully pulverizing them in water, 

 that what appear to the eye simply as white grains were, in fact, 

 well-preserved fossils. He obtained about a thousand of these 

 from each pound weight of chalk, some being fragments of mi- 

 nute corallines, others entire Foraminifera and Cytherinse. The 

 annexed drawings will give an idea of the beautiful forms of 



Cyiherince and Foraminifera from the cliallt. 



Fig. 19. Fig. 20. Fig. 21. Fig. 22. 



Cytherina. Portion of Lenticulina, Lam. Discorbis. 



J^odosaria. {Operculina, D'Orb.) 



many of these bodies. The figures a a represent their natural 

 size, but, minute as they seem, the smallest of them, such as a, 

 Fig. 22., are gigantic in comparison with the cases of infusoria 

 before mentioned. There is, moreover, good reason to believe 

 that the chambers into which these Foraminifera are divided are 

 actually often filled with hundreds of infusoria ; for many of the 

 minute grains which they contain, and which compose the envel- 

 oping chalk, have been observed, under a powerful microscope, 

 to consist of circular discs, like the articulations of Gaillonella, 

 before represented in Fig, 18. The bodies alluded to were cal- 



