186 



COOKE : JACKSON AND VICKSBURG DEPOSITS 



Loss on ignition 



Tricalcic phosphate 

 Ipsoluble 



92.08 

 7.68 

 0.22 



99.98 



These analyses show that the inorganic matter of these minute 

 creatures consists ahnost entirely of calcium phosphate, although 

 more refined analyses on larger quantities of material would 

 doubtless show small percentages of other things. So far, how- 

 ever, it seems that these very small organisms effect what is 

 perhaps a primary concentration of the traces of phosphorus 

 that exist in sea water, and so, as food for the larger animals, 

 they furnish the material from which the skeletons of marine 

 vertebrates are built. It is a familiar fact that vertebrate 

 skeletons consist largely, although not exclusively, of calcium 

 phosphate. 



GEOLOGY. — Correlation of the deposits of Jackson and Vicks- 

 burg ages in Mississippi and Alabama.^ Charles Wythe 

 Cooke, Geological Survey. 



The deposits of Jackson and Vicksburg ages in Alabama are 

 usually referred to a single formation, the ''St. Stephens lime- 

 stone," although many writers have pointed out differences 

 between the upper and the lower parts. Smith and Johnson'^ 

 divided the "St. Stephens limestone" into three members which 

 correspond roughly to the major divisions adopted in this paper, 

 and incomplete studies in western Alabama led Vaughan^ to the 

 opinion that more detailed investigation would differentiate the 

 Jackson from the Vicksburg. 



This paper summarizes the results of field studies on the 

 stratigraphy and paleontology of the ''St. Stephens limestone" 



1 Published by permission of the directors of the U. S. Geological Survey 

 and the Mississippi Geological Survey. 



2 Smith, E. A., and Johnson, L. C., U. S. Geol. Survey Bull. 43: 20. 1887. 

 ' Vaughan, T. W., U. S. Geol. Survey Prof. Paper 71: 738, 739. 1912. 



