Williams] THE HERCYNIAN FAUNAS. 81 
chison furnishes important new evidence bearing upon the question of 
the exact boundary between the Silurian and Devonian systems in 
North America. 
The discussion of the Hercynian problem has resulted in the placing", 
by several of the best continental European paleontologists, of the 
Silurian-Devonian boundary below the Hercynian fauna. Kayser, 1 
followed by others, has adopted the opinion that the American equiva- 
lent of the Hercynian fauna is to be found in the Lower Helderberg. 
Dr. J. B. Clark and Mr. Schuchert 2 have attempted to prove, on 
paleontologic grounds, that the Lower Helderberg fauna has a Devo- 
nian u aspect," and, trusting to their theories, have proposed to classify 
the formations containing the typical Lower Helderberg faunas in the 
Devonian system. 3 
When Professor Kayser's paper first appeared the writer was struck 
with the force of his paleontologic argument for classifying the Lower 
Helderberg and Hercynian faunas together, but was not then satisfied 
with the proof of the Devonian age of all the faunas so classified. 
When Dr. Barrois's paper on the Erbray faunas appeared, 4 it was 
gratifying to find confirmation of this opinion. 
Dr. Freck's papers 5 were also emphatic in claiming a Devonian age 
for the Hercynian, and the combined evidence of these gentlemen (and 
others taking part in the discussion) pointed very strongly to the 
conclusion that we must drop our Silurian-Devonian boundary below 
the main part of the Lower Helderberg if we would adopt European 
(continental) usage. 
The similarity of the Gaspe section to the typical Welsh sections of 
the Silurian system, running up to the base of the Old Red sandstone, 
gave me hopes that a study of the sections in northern Maine might 
reveal some faunas representing the upper part of the Silurian more 
closely than do the faunas of New York. As the fossils, of Maine 
were studied a transition fauna was found which throws considerable 
light upon the exact position of the boundary plane between the two 
systems, Silurian and Devonian, in our North American rocks. 
The fauna referred to is in the Chapman sandstone. A preliminary 
examination of it has revealed its close correlation with the Ludlow 
Tilestone fauna of Murchison, and its still closer relation to the Upper 
1 Die Fauna der altesten Devon-Ablagerungen des Harzes: Abhand. geol. Specialkarte Preussen, 
etc., Vol. II, Pt. IV, 1878, pp. 284-285. 
2 The nomenclature of the New York series of geological formations: Science, Dec. 15. 1899, new 
series, Vol. X, pp. 874-878. 
3 See paper read at the Geol. Soc. America, Washington, December. 1899. 
4 Fauna du Calcaire D'Erbray, by Charles Barrois: Mem. de la Soc. geol. du Nord, Vol. Ill, April, 
1889. 
sUeber das rheinische Unterdevon und die Stellung des " Hercyn," by Fritz Freck: Zeitschr. 
Deutsch. geol. Gesell., Jahrg. 1889, pp. 175-287, etc. 
Bull. 165 6 
