When discussing the stability of iron oxides, one must invariably deal with oxygen fugacity as a variable. To many geophysicists the importance of this variable in determining the stability and composition of oxides is not immediately apparent. Indeed, even within the petrologic community there are many misconceptions about what oxygen fugacity is and how it applies to rocks. The purpose of this chapter is to introduce the concept of oxygen fugacity so that later discussions within this book that use oxygen fugacity as a variable will be more comprehensible. <...>

Marine Minerals was first published in 1979 as Volume 6 of the series entitled "SHORT COURSE NOTES." In 1980 the Mineralogical Society of America changed the name of the series to "REVIEWS IN MINERALOGY," and for that reason this, the second printing of Marine Minerals has been reissued under the new banner. Only minor corrections have been made. The reader's attention is directed to the titles of other volumes published in the "REVIEWS" series, as listed on the opposite page. <...>

When describing, two years ago, the Blake Collection of Ammonites 'from Kachh (Cutch), the writer (1924, p. 1) regretted that owing to the fact that he had not been able to re-examine "\Vaagcn's types, the affinitiefi of some of the oft-quoted Kachh species would have to remain 1mcertain· The kind offer, soon after, by Dr. E. H. Pascoc, the Director of the Geological Survey of India, to unde1take the revision of the Ammonite fauna of Kachh, was therefore eagerly accepted by the writer. l\lr. Oldham's anticiJlation of 1873 that Waagen's work would turn out to be one of the most important contributions to the Cephalopod palreontology of the Upper Jumssic formations ever issued, was completely realised, and the writer feels deeply grateful to Dr. Pascoe for entrusting him with the revision of so important a fauna.  <...>

This publication consists of tite revision of an abundant and well preserved flora. Thís flora was collected in the region known as El Consuelo, Iocated in the Mixteca Alta, State of Oaxaca, Mexico, and studíed by Wieland in 1914. The purpose of this revision was múltiple. From the observation of the material and the Illustrations of the monograph (Wieland, 1914-1916), it is evident that Wieland applied a stríct monotypic criterion.