wiuiams.} NUTTALL, OWEN. 137 



iugly calcareous ; and the strata representing the Devonian system be- 

 come reduced in amount, and less varied in composition, and contain a 

 limited fauna ; and, finally, in Alabama, Tennessee, Arkansas, and 

 southern Missouri, a black shale only a few feet in thickness, with Lin- 

 gulas and rarely other fossils, is all that represents the complex stratig- 

 raphy and paleontology of the Devonian of New York. The " Black 

 shale " has consequently assumed an important role in the correlations 

 of the Mississippian series. 



The upper termination of the series is marked by the more or less 

 rapid change from calcareous to coarse arenaceous deposits, indicative 

 of elevation and shore line sedimentation. 



In the Appalachian province, Rogers's "Serai Conglomerate" has 

 been adopted as the base of the Pennsylvania series of Coal Measures, 

 butin the Mississippian province, although the coal bed > are preceded by 

 a greater or less thickness of arenaceous sediments, the delimitation 

 between the Mississippian and the Coal Measures, as we shall see, is 

 not yet drawn with any great degree of precision. 



Thomas Nuttall, in the year 1821, in the article referred to on p. 25, 

 made the first allusion discovered in our literature to the limestone 

 rocks of the Mississippi Valley as a formation possessing common char- 

 acteristics. These limestones he rightly interpreted by recognizing in 

 them the fossils of Martin's Petrifacta Derbiensis. It is not probable 

 that he, any more than many geologists who immediately followed him, 

 recognized the distinction between the true Carboniferous limestones 

 and others of Silurian and of Devonian age. The fact that the lime- 

 stones which he described as forming the calcareous platform of the 

 Mississippi are conspicuously of Lower Carboniferous age, and that 

 for years they went under the names " Mountain limestone," " Carbon- 

 iferous limestone," and " Cliff limestone," is sufficient reason for giving 

 special consideration to these Mississippi Carboniferous limestones. 



It was D. D. Owen, however, who devoted careful study to the Mis- 

 sissipian series and first described and elaborated the details and pro- 

 posed a distinct nomenclature and classification. His earlier views on 

 the subject are found in the reports of the geological survey of Indi- 

 ana. The first and second annual reports were published in 1839. 1 



In the first report Owen gave the general outlines of the system then 

 in use in Europe as expressed in De la Beehe's Manual, and constructed 

 a section representing his interpretation of the rocks " along a line from 

 Terre Haute running southeasterly toward that part of the Alleghany 

 range which divides Tennessee from North Carolina," thus : 



Bituminous coal formation. 



Mountain limestone. 



Grauwacke. 



Crystalline and inferior stratified rocks. 



1 Report of a Geological Reconnoissance of the State of Indiana made in the year 1837 in conformity 

 to an order of the legislature. By David Dale Owen, M. D., geologist of the State, pp. 34, 1839. 



Second Report of a Geological Survey of the State of Indiana made in the year 1838. By David 

 Dale Owen, 1839. 



