CONTENTS 
V 
Editorial : 
Judicial Attitude in Geological Criticism, 311; Most Produc¬ 
tive Field in Historical Geology, 319 
Paleontological Geology : 
Anatomy of Early Trilobites, by C. D. Walcott, 321; Extinc¬ 
tion of the Tetracoralla, by G. M. Hall, 322; Lowering of Life’s 
Record in the Abyss of .Time, by C. Keyes, 327; Occurrence 
of Oldest Known Trilobites, by C. D. Walcott, 329; Lilley and 
Devonic Fishes, by E. M. Kindle, 330; Lunar Petrifactions, 
by F. W. Sardeson, 331 
Mining Geology: 
America’s Mountain of Gold, by C. Keyes, 335 ; Origin of East 
Mesabi Magnetitic Ores, by F. F. Grout, 337; First Mention of 
Ores of Zinc in America, by C. Keyes, 340; Location of Wis¬ 
consin Road Metal, by E. E Bean, 341; New Borate Field in 
Nevada, by C. Keyes, 343; Potash Wells in Western Texas, by 
J. A. Udden, 344; Recovery of Low-grade Magnetitic Ores in 
North Carolina, liy J. H. Pratt; Circulatory Cycles of Ore- 
bearing Waters, by C. Keyes, 347; World’s Oil Reserves, by 
C. Keyes, 350; Verity of the Pipe Vein, .by C. Keyes, 352 
June Number 
Rightful Demesne of Petrology, by Charles P. Berkey . . 353 
Oldest Known Peccary from America, by Harold J. Cook . . 357 
SuMMiTAL Plain of tfie Colorado Rockies, by Charles Keyes . 359 
Age of Talladega Slates of Alabama, by William F. Prouty . 363 
Origin of Bolivian Copper Deposits, by J. T. Singewald, Jr., and 
Edward W. Berry.367 
Vadose Ore Deposition, by Charles Keyes.379 
Editorial : 
Geology in Bolshevik Land, 393; Beginnings of Economic 
Geology in America, 395 
Mineralogical Geology: 
Geologic Setting of Colemanite Deposits, by C Keyes, 399; 
Sedimentary Nature of Colemanite-bearing Beds, by C. Keyes, 
399; Contemporary Formation of Commercial Borates, by C. 
Keyes, 401; Interior Seas of the Arid Region, by C. Keyes, 
402; Marine Origin of Boraciferous Terranes, by C. Keyes, 
403; Vein Character of Colemanite Deposition, by C. Keyes, 
407; Vein Attitude of Borate Beds, by C. Keyes, 408; Forma¬ 
tion of Borate in Desert Playas, by C. Keyes, 410; Faulting 
of Colemanite Beds, by C. Keyes, 411; Possible Secondary 
Character of Bedded Colemanite, by C. Keyes, 414; Death 
Valley Boraciferous Terranes, by C. Keyes, 416 
Stratigraphical Geology : 
Precordillera of San Juan and Mendoza, Argentina, by R. L. 
Collins, 417; Stratigraphic Sequence of Southern Patagonia, 
by W. R. Smith, 418; Basic Tertic Conglomerate in Black 
Hills, by H. J. Cook, 422; Limitation of Cretacic Formations 
in Southwestern Iowa, by C. Keyes, 424; Rio Grande Carbonic 
Province, by C. Keyes, 425 
Index .427 
