2fj CARBONIFEROUS AMMONOIDS OF AMERICA. 



St. Louis-Chester: Goniololioceras, GlyphioceraK, Goniatites s. str., Gaslriocirns, Piiraleijori'ras, 

 Pronoriies, Nomismoceras?. 



Lower Coal Measures: GliijMoceras, Gastrioceras, Faraler/ocenig. 



Middle Coal JIeasures: Popannmras, Xeoicocerm, Prolecanites? , Glyphioceras, Goniatites s. str., 

 Gustrinceras, Paralegoceras. 



Upper Coal Measures: Milleroceras, Glyphiocerasf , Gastrioceras, Schistocercif, SJiunmnliti'.i, Puni- 

 lerjoceras, A<jalhiceras, Popanocercts, Sclmchertites, Goniohhoceras, Dimorphoceras. 



Permian: Paralegocenis, Popanoceratt, Waar/enocerax, Medlicottia. 



The association and range ot" the genera of tlie Uj^per Coal Measures 

 are approximately the same as in the Uralian of Eurojie, except that in 

 Europe the true ammonites are not known below the Permian. 



Popanoceras, Shumardites, and ScJmchertites would be classed by any- 

 one among the ammonites, on account of their complex septa, while Schisto- 

 ceras might justly be placed under the same group, on account of the large 

 number of lobes and the forward-pointing siphonal collars. 



While nearly all the characteristic European genera are present, some 

 are extremely rare, represented by a single species, as Agathiceras, Dimor- 

 phoceras, Nomisnioceras, and Pericyclus; others ha\-e a different range in 

 America from that in Europe. Dimorplioceras apj^ears first in Europe in the 

 Vise horizon, but in America is unknown until the Upper Coal Measui-es, 

 or Uralian. Fojjaiiocerns is known in Europe only in the Permian, but in 

 America it occui-s in the Middle and Upper Coal Measures. Gastrioceras 

 and Paralegoceras do not appear in Europe before the middle of the Coal 

 Measures, but in America they are known in the St. Louis-Chester. Pro- 

 dromites, Goniolohoceras, Schistoceras, Shumardites, and Schuchcrtites are not 

 yet known in the European region. 



These differences of range and association give us hints as to the 

 region where some of these forms originated, but the information is too 

 indefinite to allow any jjositive statements as to the faunal geography of 

 that time. This much is certain: At least periodically there was easy 

 intermigration between the American and the Eui'opean w\aters, foi' the 

 community of genera, and even of species, is too great to be explained by 

 any other hypothesis. 



