62 UPON KOSSIIi INFUSORIA. 



the ribsj but also the six apertures of the armour of Navicula viri- 

 dis, the four apertures of Gaillonella, the two apertures of Gompho- 

 nema, &c. The stone of the Isle of France only appears to contain 

 a preponderance of salt-water animals. The few yet unknown 

 forms may be considered very appropriately as still existing, al- 

 though yet undiscovered, animals. What is most striking, is the 

 preponderance of individual species which thus characterize the dif- 

 ferent stones ; for instance, the Navicula viridis in the siliceous 

 concrete (kieselguhr) of Franzensbad, BaciUaria vrdgaris in that of 

 the Isle of France, and Synedra capitala in the pulverulent silica 

 (bergmehi) of Santa Flora. The still existing ones are more mixed, 

 and live only about and upon plants, on which they feed. 



Purchasable foliaceous tripel (Blatter tripel) likewise shewed that 

 its mass equally consisted of infusoria. The polishing slate of Bilin, 

 in Bohemia, which forms entire beds, I have discovered to consist 

 almost exclusively of infusoria, which may be ascribed to the genus 

 Gaillonella (G. dislans). Podosphenia 7iana, n. sp., Navic. scal- 

 prum ? and Bacillai ia vulgaris (the last are still living salt-water 

 animalculse), present themselves only occasionally ; the first alone is 

 sometimes in equal abundance with the Gaillonella. There are 

 found in the same polishing slate the impressions of plants and an 

 extinct species of fish — Leuciscus papyraceus of Bronn, accord- 

 ing to Agassiz, In the adhesive slate of IMenilmontant I found but 

 thin doubtful traces of the altered Gaillonella dislans. An indivi- 

 dual of this species, which forms, almost without any connecting 

 substance, the polishing slate, is 2^'" large ; many are smaller, and 

 one cubic inch of this stone contains 41,000,000,000 (! ! — Ed.) of 

 these animals. 



