24 abstracts: geology and paleontology 



different" electrolyte. Pyrite is so inert to many solutions as to func- 

 tion like an " unattackable" electrode, thus making oxidizing and 

 reducing solutions available for producing electric currents in ore 

 deposits. Differences in polarization were detected, however, and 

 measured when different minerals were emploj^ed as anodes and 

 cathodes. R. C. W. 



GEOLOGY. — Geology of the phosphate deposits northeast of George- 

 town, Idaho. R. W. Richards and G. R. Mansfield, with preface 

 by H. S. Gale. U. S. Geological Survey Bulletin No. 577. Pp. 74. 

 1914. 

 The area discussed lies in southeast Idaho and includes many for- 

 mations ranging in age from lo\^'er Carboniferous (Madison limestone) 

 to Quarternary (chiefly alluvium and basalt). It is traversed by the 

 great Bannock Overthrust, the plane of which is warped and partially 

 eroded. The older rocks constituting the upper block are folded into 

 a series of anticlines and synclines with axes trending slightly west 

 of north. Large bodies of phosphate rock occur in the synclines. The 

 younger rocks of the lower block are also underlain by phosphate. 

 Salt deposits occur along the line of the Bannock Overthrust. 



R. W. R. 



GEOLOGY AND PALEONTOLOGY.— Cretoceows deposits of the east- 

 ern Gulf region, and species of Exogyra from the eastern Gulf region 

 and the Carolinas. Lloyd William Stephenson. U. S. Geo- 

 logical Survey Professional Paper No. 81. Pp. 71. 1914. 

 The paper is a preliminary general account of the character, dis- 

 tribution, and age relations of the Cretaceous deposits of the eastern 

 Gulf region, followed by detailed descriptions of the species of Exogyra 

 from this region and the Carolinas. It is shown that marine Upper 

 Cretaceous deposits composing certain great formations merge along 

 the strike into marine deposits of different character in such a manner 

 that the relative ages of the deposits in different parts of the area can 

 not be determined by stratigraphic sequence alone. Two major faunal 

 zones characterized respectively by Exogyra ponderosa Roemer and 

 Exogyra costata Say, and two sub-zones characterized respectively by 

 the genus Mortoniceras and the species Liopistha protexta Conrad, are 

 recognized; an unnamed zone in the lower part of the Eutaw formation 

 in the Chattahoochee region is also indicated. Within each of these 

 zones and subzones are found many other species of restricted range. 

 Paleontologic means is thus afforded of establishing the age relations 

 of the deposits. 



