260 C. SCHUCHKRT — LOWER HELDERBERG— ORISKANY FORMATIONS 



by Kayser,* is brought into the comparison, a fauna is met which also 

 Btrongly recalls the Oriskany as well as the Lower Helderberg. 



The brachiopods are the predominating fossils, with the long-hinged 



species of Spinier in well developed forms. The Oriskany -types are 

 S. decheni, S. ilsse (the representatives of the American S. murchisoni Cas- 

 telnau and S. arrectus Hall); S. nerei, var., S. hercyniae (closely related to 

 S. cumberlandise and S.tribulis). Another Hercyn Spirifer, S. bishofi, may 

 l>e compared with the Oriskany species S. arenosus, one of the most 

 characteristic Spirifers in the introduction of the plicated fold and sinus. 

 Of Lower Helderberg Spirifers, & macropleura may be compared with the 

 Hercyn S. jaschei and S. sp. (figure 6 of plate xxi). On the other hand, 

 such species as S. togatus and S. sericeus recall S. radiatus, clearl}' a rem- 

 nant of the Siluric fauna, but not of that age because of the far greater 

 size attained by these forms. 



Another Oriskany reminder is Meganteris figured by Kayser. This 

 species is far larger than M. ovalls and as large as RensselseHa ovoides, a 

 very closely related form. However, since it is the only terebratuloid 

 in this, the true Hercyn fauna, the paucity is most marked when com- 

 pared with the Oriskany or even with the Lower Helderberg. The 

 Hercyn pentameroids are in harmony with those of the Lower Helder- 

 berg, while the rhynchonelloids are unlike any American facies. In a 

 number of species the latter appear to be ancestors of Hypothyris cuboides 

 of the Middle Devonic. 



When the Hercyn Brachiopoda of the meristelloid family is examined, 

 there is seen to be a marked paucity of species, especially when com- 

 pared with the Lower Helderberg. The same is true of the Retzias, and 

 particularly the orthoids. On the other hand, the presence of Atrypa 

 aspera in the Hercyn is that of a form first appearing in the Corniferous 

 or Middle Devonic. 



The strophomenoids are non-committal, while the presence of several 

 species of Chonetes, some of which attained a size above the average, 

 denotes the Middle Devonic. Craniella is also rather indicative of a 

 horizon above the Lower Helderberg. 



From this summary of the brachiopods the conclusion is reached that 

 the Hercyn species, if of one fauna, indicate an age not as old as the 

 Lower Helderberg and probably not much younger than the later 

 Oriskany. 



With few exceptions, the Hercyn trilobites are those of the Lower 

 Helderberg and Lower Oriskany. The exceptions are the presence of 

 Harpes, a remnant of Ordovicic or Champlainic times, and the occur- 

 rence of Cryphseus, a genus first appearing in America in the Middle 



*Die Fauna der altesten Devon-Ablagerungen des Harzes, Abh, /.. geolog,, Specialkarte von 

 Preussen, Band ii, Heft 4, 1878. 



