Ehrenberg on Infusoria in Igneous Rocks. 417 



infusorial iron, 5 &c. ; but all these long additions to ordinary expres- 

 sions are manifestly inconvenient, and the same difficulty occurs 

 with regard to the names ' tuff,' ' volcanic conglomerate,' e pumice,' 

 'phonolite,' &c. 



The author then suggests as a convenient nomenclature, that we 

 should denominate those minerals which do not exhibit either among 

 their actual component parts or from the conditions of their aggre- 

 gation any marks of organic existence, c elementary tripoli,' * ele- 

 mentary limestone,' c elementary pumice,' &c, or together, Stoechi- 

 olite (elementary rock), in contradistinction to the other group, 

 which we may designate Bioiite (organic rock). 



True Biolites, however, are not those rocks and formations which 

 simply contain fossils, but those which are deduced from and con- 

 sist of agglomerations of organic bodies either absolutely or essen- 

 tially, and which merely contain inorganic particles here and there 

 distributed amongst them. By this name however we may correctly 

 designate infusorial polishing slate, tripoli, the whole mass of polytha- 

 lamial chalk, coal, &c. Fossil shells, corals and bones are sometimes 

 indeed so far components of rocks as to form entire masses, but they 

 are generally extraneous, although often characteristic contents. 



On the other hand, the true well-defined elementary rocks 

 (Stoechiolites) are those which have no essential and original rela- 

 tion with organic existence, and only occasionally and accidentally 

 contain fossil organic bodies. 



For those rocks of organic origin which have not been subse- 

 quently modified by volcanic agency it would be both convenient 

 and definite to employ the more special name Hydrobiolite, while 

 those, on the other hand, which have been so altered, we might call 

 Pyrobiolite, or pyrobiolitic rock, earth, or formation. And if it 

 should seem that a still further subdivision would be useful, we 

 might describe such rocks as the paper-coal (dysodil), the Bilin 

 polishing slate, mammillated slate, and other freshwater substances of 

 this kind, Hydrozoolite, while coal, &c. might be called Ilydrophy- 

 tolite. So on the other hand we might designate white chalk and 

 the Sicilian marly chalk, as well as the Virginian infusorial marl, 

 Halizoolite (from its relation to marine organic life). 



