THE 
AMERICAN GEOLOGIST. 
Vol. XXXII. DECEMBER, 1903. No. 6. 
THE DEVONIAN ERA IN THE OHIO BASIN.* 
By Edward W. Clatpole. 
V. ANCESTRY OF THE DEVONIAN VERTEBRATES 
OF THE APPALACHIAN GULF. 
Throughout the vast strata of Cambria, Ordovicia and Si- 
luria, with all their crowded fossil forms, only the scantiest 
traces have been found in America of fossils that indicate ver- 
tebrate affinity. Such remains have long been known in Europe 
where, especially in England, different species of the pteras- 
pidians are abundant in the uppermost Silurian beds The 
discovery, therefore, by the writer in 1883 of similar fossils 
(Palseaspis) in rocks of the Salina group in middle Pennsyl- 
vania was of great interest by establishing a correlation of the 
strata on both sides of the Atlantic in this respect. Indeed, the 
oldest of the specimens there found and described by myself, f 
coming as they did from the Clinton strata, are of somewhat 
older date than even Scaphaspis ludensis of England, the soli- 
tary specimen yet known from the Lower Ludlow of that 
country. But the Pteraspis, Scaphaspis, Holaspis, etc., of the 
east and the Palaeaspis of the west are so closely alike that they 
must also be as closely allied. At the same time their struc- 
ture is so peculiar and so different from that of any other fishy 
that it is difficult to trace any line of genetic connection between 
them and their successors. If connecting links exist the) must 
exist elsewhere, for their occurrence in the Ohio basin, though 
still possible, is scarcely probable. 
* Continued from page 322. 
* Quart. Jour, of the Geol. Soc. of Lond., 1885 and 1892. 
