APPLICATION OF TERM SILURIAN 245 



the formations below are as intimate as with those above ; while in the Northern 

 and Middle States, the Oriskany sandstone bears in its fauna a closer relation to the 

 lower than to the overlying formations."* 



It will be shown that the Lower Heklerberg has its equivalent, faunally, 

 in Barrande's etage F 2 . as found at Koniepruss,in Bohemia, and that, in 

 the Rhine section, German geologists have for this formation a fixed 

 place in the Lower Devonic. 



In his "Synopsis of American fossil Brachiopoda. r published three 

 years ago by the U. S. Geological Survey ,f the writer included all Lower 

 Heklerberg and Oriskany species in "Table VI, Devonian Brachippoda," 

 as " Eodevonian." Apparently no one has noticed this radical departure 

 from accepted American standards; at least, no one has pointed it out 

 or given reasons why these forms are not of Devonic age. 



Silurian of Murchison J 



APPLICATION OF THE TERM BY GEOLOGISTS 



In 1835, the term Silurian w r as first applied by Murchison to a series 

 of formations well developed in Shropshire, England, a " region once 

 inhabited b} r the British tribe of Silures;" hence the name. 



" From the base of the Old Bed sandstone, he was able to trace his Silurian types 

 of fossils into successively lower zones of the old ' Grauwacke.' It was eventually 

 found that similar fossils characterized the older sedimentary rocks all over the 

 world, and that the general order of succession worked out by Murchison could 

 everywhere be recognized. Hence the term Silurian came to be generally employed 

 to designate the rocks containing the first great fauna of the Geological Record." 



At first the Silurian not only included what is now known as Lower 

 Silurian, or Ordovicic, or Champlainic, and Upper Silurian, or Siluric, 

 but also much of the Cambrian of Sedgwick. " The controversy regard- 

 ing the respective limits of the Cambrian and Silurian formations sur- 

 vived the lifetime of the two great antagonists.'^ 



The present work, however, has no bearing on the lower limit of Mur- 

 chison 's Silurian, but aims to determine w T hat constituted the upper limit 

 of his " Upper Silurian " and the lower limit of his *' Devonian." 



Regarding the Upper Silurian, Murchison, in 1854, in his " Siluria," 

 wrote as follows : 



"When, on the contrary, we follow the same deposits from North and South 

 Wales to the exemplar tracts of Herefordshire and Shropshire, where the Upper 



* For further remarks see p. 291. 



f Bulletin no. 87. 



J See Geikie's Text-book of Geology, 3d ed., 1893, p. 737. 



§ Geikie, p. 737. 



