wiluamb.] JAMES HALL. 149 



that the Subcarboniferous fish increased greatly in size during this pe- 

 riod. In the southern extension of the Pentremital and Archimedes 

 limestone into Tennessee and Alabama, these remains are exceedingly 

 rare. 



In 1856 James Hall l read a paper before the American Association, 

 an abstract of which was published in the American Journal of Science. 

 His object was "to show that there are certain well marked subdivi- 

 sions in the Carboniferous limestone of the Mississippi Valley." 



The article appears to be a preliminary account of chapters which 

 appeared later in his Keport on the Geology of Iowa. 



In the following table are expressed the correlations which he pro- 

 posed, showing the " true order of superposition among the different 

 members of the limestone series : w 



VII. Coal Measures. 

 VI. Kaskaskia limestone, or Upper } * $ Kaskaskia and Chester, St. Mary's, 



Archimedes limestone. ) \ Missouri. 



V. Gray, brown, or ferruginous sand- ) ( Below St. Genevieve, Missouri. Be- 

 stone, overlying the limestones > of -? tween Prairie du Rocher and Kaskas- 

 of Alton and St. Louis. ) ( kia, Illinois. 



IV. " St. Louis limestone," or " Con- l fS St. Louis ; highest beds below Keo- 

 cretionary limestone." $ c kuk. Alton ; St. Genevieve. 



III. "Arenaceous bed," Warsaw or ) « < Warsaw and above Alton, Illinois; 

 Second Archimedes limestone. $ { Keokuk, Iowa. 



" Magnesian limestone," — Spergen Hill, Bloomington, Iowa. 



Beds of passage, soft shaly or marly bed with geodes of quartz, chalcedony, etc. 



II. Keokuk limestone, or Lower Ar- ? « ( raAl ,„ l , /v_. T11 . , 



chimedes limestone. \ of \ Keokuk > Q uinc y, IUmois, etc. 



Beds of passage, cherty beds 60 to 100 feet. Rapids above Keokuk. 

 I. Burlington limestone }of { %^% ^i^^?' ^"^ 



The formations I to VI, inclusive, constituted the " Carboniferous 

 limestone ;" next below them he reported the 



Oolitic limestone and argillaceous > i Burlington, Iowa; Evans Falls, and 

 sandstone of the age of the Chemung \ of I H anSibal, Missouri, 

 group of New York. ) ( 



He correlated the " Argillo-calcareous group n of Owen and the 

 "Chouteau limestone" of Shumard and Swallow with the "Chemung 

 group" of New York, stating that "the higher beds contain the same 

 fossils as the Chemung group of New York and elsewhere, and have 

 been carefully traced throughout the intermediate space." 2 



He thought the "green shale" of the Burlington section and the 

 "ash-colored earthy marlites" of Evans Falls "should be referred to 

 the Portage group. * * * It is likewise probable that the litho- 

 graphic limestone of Prof. Swallow will be found more closely allied 

 to the Hamilton than to the Chemung group." 



The name "Burlington limestone " was proposed to include what 

 Owen had called the " encrinital group of Burlington," and " reddish- 



1 Hall, James; On the Carboniferous limestones of the Mississippi Valley. (Abstract.) Am. Jour. 

 Sci., vol. 23, 1857, pp. 187- 203. 

 'Ibid., p. 189. 



