Marylaxd Geological Survey 81 



derivatives. The writer therefore concludes that the Hehlerbergian has 

 a fauna unlike the Siluric, but one in harmony with the Devonic and its 

 position near the base of that system " (pp. 277, 278). 



In regard to the Oriskauy, it was stated: "As a rule the Oriskany 

 formation consists of littoral deposits, often of a very coarse nature. 

 When it is remembered that, in addition to this fact, the formation has 

 very limited, usually linear, exposures, it is remarkable that its fauna 

 should consist of 185 species. Chief among these are the brachiopods, 

 of which 97 species are known. They are the most abundant fossils, and 

 their generally larger growth at once marks the Oriskany as one of the 

 easily recognized American Paleozoic faunas. 



" In spite of the characteristic expression of the Oriskany fauna, it is 

 remarkable that it should be so intimately connected both with the Helder- 



berg and with the Onondaga Of the 185 species included in the 



Oriskany fauna, 31, or 17 per cent, come from the Helderbergian, while 



54, or 35 per cent, pass into the Onondaga These figures prove 



that the Oriskany is intimately connected with the Helderbergian and 

 Onondaga. This is still more forcibly brought out when it is stated that 

 of the Becraft fauna, the one immediately beiieath the Oriskany, not less 

 than 27 per cent of its species pass into the Oriskany. All these figures 

 are in strong contrast with the very few species which pass from the 

 Niagaran and Cayugan formations into the Helderbergian. Of these 

 there are 9 persisting forms, or about 2 per cent, in a fauna of 459 de- 

 scribed species " (p. 291) . These figures are now all enlarged by the more 

 recent work of Clarke,' thus more intimately binding the Helderberg and 

 Oriskany, these with the Middle Devonian, and separating both series 

 more distinctly from the Silurian. 



The histor}' of the American Lower Devonian is shown in the accom- 

 panying table : 



'The Oriskany Fauna of Becraft Mountain; and Early Devonic History of 

 New Yorlt and Eastern North America. Memoirs 3 and 9, N. Y. State Mas., 

 1900 and 1908. 



