80 The Lower Devonian Deposits of Maryland 



system it should be referred to, and the Devonian began with the Schoharie 

 at the base of the Onondaga. 



Hall * again maintained this view in 1861, when he published the text 

 of the third volume of Paleontology of New York, and this arrangement 

 was sustained until 1889, when Clarke ^ questioned Hall's classification. 

 In his paper entitled The Hercynian Question, he reviews the various 

 memoirs and discussions relating to the Lower Devonian faunas of Europe, 

 and in the light of the results attained he then analyzes the Helderberg 

 faunas, stating : " The foregoing data assuredly indicate a striking de- 

 velopment in the typical Lower Helderberg fauna, of organic groups, 

 which in their culmination are characteristic of the Devonian. This con- 

 sists not merely in the inception here of Devonian types In addi- 

 tion we meet here certain climacteric features of critical value, demon- 

 strating equivalence with faunas whose age may be considered now as well 

 established" (p. 435). 



In 1900, the writer' restudied the entire Lower Devonian faunas of 

 America, listing 459 Helderberg species. But 16 of these, or about 3| 

 per cent, are derived from the Silurian. The New York Helderberg fauna 

 has 397 forms, and of these more than 9 per cent pass into the Oriskany. 

 These figures have since been increased. His final statements were: 

 " From the foregoing summary of the Helderbergian fauna it is evident 

 that most of the characteristic Siluric genera of trilobites, brachiopods, and 

 erinoids are there absent On the other hand, in some of the trilo- 

 bites, Bryozoa, and pelecypods, many of the gastropods, but more par- 

 ticularly in the diversified brachiopods, are met organic groups, which 

 in their culmination are characteristic of the Devonic. It cannot be 

 denied that the Helderbergian fauna has a Siluric facies, yet these types 

 either have greater differentiation in species or the forms attain a larger 

 size. The fact that nearly 9 [now known to be about 12] per cent of 

 the Helderbergian fauna pass into a generally accepted Devonic horizon, 

 the Oriskany, outweighs the evidence of a Siluric facies and siDecific 



'Nat. Hist. N. Y., Pal., vol. iii, 1S59 (text published in 1S61), pp. 32-43. 

 ' Forty-second Ann. Rept. N. Y. State Mus., 1889, pp. 408-437. 

 ' Schuchert, Bull. Geol. Soc. America, vol. xi, 1900, pp. 241-332. 



