Devonian Era in the Ohio Basin. — Claypole. 83 
"The Tully limestone contains none of the Tully fossils found in 
New York, but merely the common Hamilton forms, as identified -by- 
Prof. Claypole:" 
Atrypa reticularis, Ambocoelia umbonata, 
Spirifera Hmbriata, Spirifera ziczac, 
Chonetes setigerus, Phacops rana. 
Dalmanitcs colli teles. 
Evidently, therefore, the Tully limestone is only a local de- 
posit in the north-central part of the Appalachian gulf where, 
for the time, mechanical sediment was lacking and an oppor- 
tunity for calcareous deposition recurred. This was probably 
due to a low level of the surrounding land when the elevation 
which had given rise to the heavy shales and the thick Penn- 
sylvania sandstones had ceased and the elevated country had 
been degraded so that the currents of the rivers were slackened 
and the erosion had become weak. 
But though it may not be difficult to account for the inter- 
vention of a small thin bed of limestone at the top of the Ham- 
ilton group in New York, yet there remain other problems less 
easy of solution. What caused the sudden and considerable 
change of fauna at the base of the Tully? What also caused 
the extinction of a great part of the Tully fauna at its summit? 
The Tully Fauna. — Xo one has studied the mid-Devonian 
fauna of northern Appalachia with greater assiduity or persist- 
ence than professor H. S. Williams, of Xew Haven, who pre- 
sented an elaborate argument on the closer relationship of the 
Upper Devonian fauna of Appalachia to the Lower Devonian 
fauna of Europe than to that of eastern America.* This was 
based on the discovery of a remarkable group of fossils on Can- 
andaigua lake showing a strong relationship to the Devonian 
fauna of Iowa, and differing widely from that of Xew York, 
in the midst of which it lay. After a careful study of the fossils 
of the Tully limestone and elimination of all the doubtful spec- 
ies, he selected a group of authentic Tully specimens which, 
from the presence among them of a form closely resembling 
Rhynchonella cuboides of Europe, he called the Cuboides 
fauna. 
Continued investigation led to the conclusion that in eastern 
America, where the Tully appears, the fauna of the Cuboides 
zone begins abruptly and from it upward all through the Up- 
* Williams. Scope of PaUeontologv, Proc. A. A. A. S., 1892, and Amkr 
Geol., Sept., 1S92. 
