336 II. S. WILLIAMS — SILURIAN-DEVONIAN BOUNDARY 



before it can be put into the Devonian system. So long as the Konie- 

 prussian fauna* is recognized to be older than any of the other Devonian 

 European faunas of the same fades, there is insufficient reason for class- 

 ing it in the Devonian. It must be regarded as Silurian or transitional 

 until it can be proven to be beyond question younger than the youngest 

 of the known standard Silurian faunas. It may be above the Ludlow 

 and still represent the Downton sandstone and Ledbury shales, which 

 are above the Upper Ludlow rock of the typical section, but are still 

 typical Silurian formations. 



(c) And, thirdly, for determining the equivalency of formations or 

 faunas in other countries, the same final reference to and comparison with 

 the standard Silurian faunas is necessaiy when doubt is present as to 

 which side of the line the fauna is to go. 



(d) In the case of the American formations the general question must 

 be determined upon a comparison of the faunas of America with the 

 original standards ; of these the upper limit of the Silurian is estab- 

 lished by typical sections and faunas ; the lower limit of the Devonian 

 seems to be fairly well established in terms of faunas of the facies of 

 sandstone and arenaceous shales, but is in question as to those of a purely 

 calcareous facies. Of the latter, the faunas of Hercyn, Erbray, F 2 Menian, 

 and G and H of Bohemia are accepted as Devonian by paleontologists 

 of Europe, but F 2 Konieprussian can not be taken as of established posi- 

 tion above the line so long as its affinities are nearly equally with both 

 the lower and higher faunas, and its exact relation to the typical faunas 

 in Wales is uncertain. 



ORISKANY FAUNA OF AMERICA EQUIVALENT TO LOWEST ARENACEOUS 

 DEVONIAN FAUNA OF EUROPE 



Taking up the second question, the determination of equivalency, 

 this is no longer a matter to be settled by precedent or priority, but b)' 

 a close scrutiny of the component species of the individual faunas and 

 their comparison with standards. 



In a general waj', the facts for America are as follows : 

 The Oriskany fauna of America has been regarded as the American 

 equivalent of the faunas of the more arenaceous formations at the base 

 of the Devonian system of Europe by De Verneuil, Sharp, Bixby, and 

 James Hall, who examined the fossils when their original classification 

 was prominently before geologists. The only doubt was as to whether 

 the Oriskany might not more properly be classified with the Lower 

 Helderberg in the Silurian. Conrad (and Hall at first) drew the bound- 



*Tlie fauna of the Konjepruser-kalk, F a , Barrande, 1846. 



