SUMMARY 299 



Schiefer of Erbray, and of the. Rhine Gedinnian, have aspects recalling 

 the Helderbergian, no well established equivalent for the latter is known 

 except that of the Bohemian etage F 2 , or Konieprussian. 



Barrande's etages F, G, and H, together with the Lower and Upper 

 Helderberg, were regarded by him as members of the Upper Silurian. 

 This interpretation is explained by the fact that Barrande included his 

 first, second, and third faunas (now Cambric, Champlainic or Ordovicic, 

 and Siluric) in one system, which he preferred to name the Silurian 

 system. In his day, the well known Devonic faunas of the typical areas 

 were those now classed as Middle Devonic. After much work and dis- 

 cussion, particularly in Germany, the opinion has now become general 

 that all Barrande's etages F, G, and H are of Devonic age. As the Hel- 

 derbergian is the equivalent of etage F 2 , or Konieprussian, it must also 

 be regarded as of Devonic, Lower Devonic, age. 



The Upper Coblenzian fauna of the Rhine correlates readily with that of 

 the Onondaga and Hamilton. As the latter faunas are intimately related 

 and the Hamilton is always regarded as of Middle Devonic age, it seems 

 natural to draw the line between the Lower and Middle Devonic, at the 

 base of the Esopus grit and Upper Coblenzian. Both these formations 

 are usually referred to the Lower Devonic. In United States the most 

 marked local break in the Devonic exists between the Oriskan}^ and Onon- 

 daga, and it is not closed by the very local Esopus and Schoharie grit. 

 In a general view this break is not so apparent, owing to the varying 

 age of the upper limit of the Oriskany in the various localities. 



Page 269 begins with a short description of the three zones of the 

 Helderbergian, and their geographical distribution. Then follows 

 a discussion of the faunal characteristics, with a complete list of the 

 species. The Helderbergian has 459 forms, of which about 2 per cent 

 come from the Siluric, while 9 per cent of the former pass into the Oris- 

 kany. It is also shown that most of the characteristic Siluric genera 

 of trilobites, brachiopods, and crinoids, fail in the Helderbergian; also 

 that the Siluric facies maintained in this fauna is modified and the 

 species have a larger individual growth, indicating post-Siluric age. On 

 the other hand, among the trilobites, Bryozoa, and pelecypods, in many 

 of the gastropods, but more particularly in the brachiopods, are met 

 organic groups, which in their culmination are characteristic of the 

 Devonic. The conclusion is therefore warranted that the Helderbergian 

 fauna is unlike that of the Siluric, being more in harmony with the 

 Devonic, and its position near the base of that system. 



A general description of the Oriskany strata and its areal distribution 

 follows, with a complete list of the named species. There are 185 forms, 

 of which 17 per cent come from the Helderbergian and 35 percent pass 



