Devonian Era in Ohio Basin. — Claypolc. 345 
These fossils are found in greatest quantity in the lower 
Carboniferous strata, especially in the Mountain limestone of 
Europe and in the equivalent beds of the southwestern states, 
and they have been considered specially characteristic of that 
horizon. Older rocks have, however, contributed a few, and 
the cladodont type has been known for years in the Devonian 
of North America, lint the specimens are scanty in compari- 
son with those of the later limestones. 
Reference to our table of the vertebrate fauna of the Appa- 
lachian gulf will show that at least a single specimen, Machae- 
r acanthus niajcr, has been found in the Corniferous limestone 
of Ohio. It is represented by a few spines only, and with a 
few other doubtful fossils, represents all the present knowledge 
of the elasmobranch fauna of the time. 
But the family was of earlier origin than the oldest De- 
vonian rocks, as is sufficiently evident from the size and 
strength of the specimens. There is direct proof of this infer- 
ence in the occurrence of elasmobranch fossils (shagreen) in 
the Ludlow limestones of England — Spagodus and Thelodus 
But during the interval little is known of the group or their 
history in Europe and in America. Should the Onchus de- 
scribed by myself from Pennsylvania prove to be elasmo- 
branch, this will carry back the hist try of the family to a much 
more remote date, and show that sharks were among the first 
vertebrates to appear in the waters of the planet. 
The Corniferous-Hamilton ( Hamilton ) is somewhat richer 
in remains of elasmobranehs. lint even here they are not 
abundant. Oracanthus. with four species described by New- 
berry from this horizon, must be canceled. This author writes 
in the monograph: (p. 33) : 
In a paper published some year- since in the Bulletin of the National 
Institute a* Washington, I described a number of fish remains obtained 
at Delaware, Ohio, by the late Dr. Mann. Among these three species 
of Oracanthus were described, viz.. (). fragilis, (). granulatus and O- 
abbrcviatns, all of which 1 now believe to be phases of the varied scutes 
of Acantholepi-. 
There remain therefore two species of Maclueracanthus, .. 
doubtful Psammodus, the enigmatical Cyrtacanthus and two 
species of Ctenacanthus to represent the Appalachian elasmo- 
branch fauna of the Corniferous- 1 lamiltnn, enough to can \ 
it through the period, but not enough to indicate abundance or 
predominance. The record of the eastern Hamilton is. yet 
