NIAGARA LIMESTONE. 339 



of the formation at Clifton, on Lake Winnebago. The fourth was 

 from the so-called sandstone near Taycheedah. The fifth, from the 

 upper layer, aud the sixth from the lower layer, at Audley's quarry, 

 in the town of Delafield (Sec. 20, S. E. J). The limestone in the last 

 named instance included many nodules of chert, which were excluded 

 from the samples analyzed, one object of the analysis being to ascer- 

 tain the chemical nature of limestone associated with well-defined con- 

 cretions of chert. The above analyses were executed by Prof. Daniells. 



It appears that in all cases, the carbonates of lime and magnesia 

 exist essentially in the proportions necessary to form dolomite, so that 

 these beds may be said to be true sedimentary dolomites, and the re- 

 maining constituents may be regarded as impurities, and are so sum- 

 med up for convenience, the water being disregarded. It will be ob- 

 served that the Taycheedah " sandstone " is remarkably pure. This 

 will be again noticed in the discussion of economic considerations. 



Life. The remains of the life of the period are very illy preserv- 

 ed, and it is only rarely that fossils can be found sufficiently well-de- 

 fined to be satisfactorily identified. In most cases, only obscure casts 

 remain. It is not to be inferred from this, however, that the life of 

 the period was actually meager. On the contrary, it was probably 

 abundant. The conglomeritic character of a portion of the beds shows 

 that the material was subjected to much grinding action by the waves 

 of the depositing seas, and makes it probable that the greater portion 

 were comminuted in the process of deposit, while the crystalline na- 

 ture of the rock suggests, that the process of crystallization may have 

 obliterated some that escaped comminution, and cavities having the 

 form of fossils show that some others have been removed by solution. 

 From the nature of the material, some of the identifications are neces- 

 sarily doubtful, and are so indicated. 



In the following table, the occurrence of the several species, at the 

 more important localities, will be found systematically and compactly 

 arranged. Students and collectors will find this a convenient form. 

 A table will be found at the close of the description of the Niagara 

 group, in which the fossils of this member are compared with those 

 of the other beds, which will also be found instructive. 



