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UPON FOSSIL INFUSORIA. 

 By C. G. Ehrenberg. 



M. C. Fischer, the proprietor of the manufactory of porcelain at 

 Pirkenhammer, near Carlsbad., has observed that the substance re- 

 sembling siliceous concrete, which occurs in the peat bogs near Frau- 

 zensbad, in Bohemia, consists almost exclusively of the armour of 

 some species of Naviculce. 



Together with this information, M. Fischer sent me a piece of the 

 siliceous mass, about 2" long, 1" broad, and |" high, as well as some 

 specimens of the peat, intreating me to ascertain the animal, and to 

 publish the result. Microscopic inspection immediately confirmed the 

 discovery of M. Fischer, that the siliceous concrete (kieselguhr) of 

 Franzensbad consisted almost exclusively of very well preserved Na- 

 viculce, with which other Bacillaria were intermixed ; and the per- 

 fect transparency of their siliceous armour, and its purity from all 

 organic matter, renders it pi'obable that an unusually intense heat 

 had purified them and amassed them together. It is improbable that 

 they should have originated at the bottom of the sea ; for the majo- 

 rity of the animals, both in form and the relative numbers of their 

 striis, correspond very accurately with those of the Nav. viridis, 

 which is found in all the fresh-water about Berlin, as well as else- 

 where. In the specimens of peat I could also recognise Naviculce, 

 yet they were generally diff"erent, though still existing species, fewer 

 in relative proportion, and the prevailing forms very different. 



Original specimens of the siliceous concrete (kieselguhr) of the Isle 

 of France and of Santa Fiora, in Tuscany, which were analyzed by 

 Klaproth, shewed that they likewise consisted almost exclusively of 

 the envelopes of infusoria of several genera of Bacillaria, yet some- 

 times of the same and almost all still living species, in conjunction 

 with rare siUceous spicula of fresh and sea-water sponges, without 

 any intervenient bindirg material. This, therefore, is an additional 

 confirmation of Kiihzing's discovery, that the armour of the Bacilla- 

 ria consists of silex. 



I myself discovered, several years ago, that the ochraceous slimy 

 substance which sometimes covers the bottom of marshy brooks and 

 moats, and which appears to have been considered as a deposit of the 

 oxide of iron, is a very delicate Bacillaria, which, at a red heat, be- 

 comes red like the oxide of iron, and contains much iron, but docs not 



