WEAVER: INVERTEBRATE PALEONTOLOGY AND HISTORICAL GEOLOGY 723 



The monumental work PaJeontologie frangaise, by d'Orbigny (1840-1860) 

 which was partly complete in 1856, presented a classification of the Jurassic 

 rocks and faunas of France, but d'Orbigny still considered that each stage con- 

 tained a specially created fauna, distinct from all others below and above. After 

 a study of the Jurassic in France and England the detailed investigations of 

 Albert Oppel, published in 1858, led to the introduction of the term "zones" for 

 time-stratigraphic units based on the occurrence of certain species which were 

 absent in beds above and below. This work was of fundamental importance for 

 future stratigraphic investigations. The lithologic similarities of the upper- 

 most Jurassic and lowermost Cretaceous rocks in the Alps made it difficult to 

 separate them. Oppel used the term "Tithonian" for the uppermost Jurassic 

 limestones and shales in the northern Alps; and the characteristic Tithonian 

 fauna has made possible the correlation of beds with similar faunas in distant 

 parts of the world. The Upper Jurassic faunas in England and Germany are 

 not everywhere characterized by Alpine species; the upper part of the Tithonian 

 group is now recognized as equivalent to the Portland Purbeck beds, the lower 

 to the Upper Kimmeridgian. 



The Jurassic rocks of both northern and southern Asia are rich in fossils, 

 which have been compared in important monographs by Waagen, Kitchin, and 

 Noetling, to both the Alpine and northern European faunas. A nearly complete 

 sequence of European faunal zones known in the Jurassic rocks of the Andean 

 trough of South America have been studied by Bodenbender, Steur, Burckhardt, 

 Gerth, Krantz, Jaworski, Leanza, and Feruglio. 



The absence of marine Jurassic rocks in eastern North America suggests an 

 interval of erosion. During the second half of the past century the Rocky Moun- 

 tain and Pacific Coast areas were investigated by several national exploration 

 surveys, including the U. S. Geological Survey, and by the Geological Survey of 

 California from 1860 to 1869. A shallow western interior sea spread southward 

 from Canada through parts of the Rocky Mountain region into Arizona but was 

 separated from the Pacific Coast embayments by a north and south axial land 

 mass which extended northward through Nevada and eastern California. Dis- 

 cussions of these rocks have been published in the numerous reports of the U. S. 

 Geological Survey, in state reports, and in the geological journals and bulletins. 

 The Jurassic marine formations of the Pacific Coast basins were described in 

 the reports of the Transcontinental Railway Surveys, of the Geological Survey 

 of California, the Geological Survey of Canada, the California Academy of Sci- 

 ences, the present State of California Division of Mines, and by numerous inde- 

 pendent authors connected with the universities. 



Cretaceous: The many papers, monographs, and maps concerning Cretaceous 

 rocks of western Europe published during the first half of the nineteenth cen- 

 tury made known the principal stratigraphic units and their classification. 

 Among the more important contributors were Leymerie, d'Orbigny, Buvignier, 

 and dArchiac in France; F. von Roemer, Hans Geinitz, and Emmanuel Reuss 

 in Germany and Austria. 



During the past one hundred years investigations of the Cretaceous of Europe 

 have involved detailed studies of the lithology and faunas of particular areas, 

 the correlation of different stratigraphic units from one area to another and 

 the establishment of faunal zones. Barrois in 1876 attempted to correlate the 



