14 



FOSSIL MEDUSAE. 



nodules Owing- to the folding and fracturing of the strata, it is impossi- 

 ble to prove that the sandstones, siliceous nodules, and calcareo-siliceous 

 nodules were deposited at the same identical horizon or formed in the same 

 period of time This is probable, but in the absence of an unbroken 

 stratum and a similar fauna it can not be proved. 



The shale is hard and compact in its unweathered portions. 



CHEMICAL CHARACTER OF THE NODULES AND SHALE. 



Partial analyses, by Dr. H. M. Stokes, of the Geological Survey, of 

 the dark inner portion and the red outer portion of one of the fossil medusae 

 (nodules) give the following- results: 



Analyses of portions of a fossil medusa. 



The following analysis of the shale, by Dr. Stokes, shows that the mud 

 or sediment in which the medusae were buried was highly siliceous: 



Analysis of the Coosa shale. 



a FeO approximate only, owing to presence of organic matter. 

 b Represents only the carbon of the organic matter. 

 c Includes water from oxidation of organic matter. 



