346 The American Geologist. December, 1903. 
more meagre, as the tables of the Devonian vertebrates will 
show. 
In the overlying black shale, Huron or Genesee-Portage 
the elasmobranch history is again broken, the solitary Goniodus 
hertseri of Ohio alone representing it there. 
The same break continues through the Erie shale (Che 
mung) a Cladodus (C. carinatus) from Warren, Pennsylvania 
— the earliest known cladodont — being the sole member of th< 
elasmobranch class thus far recorded. 
Until within the past few years the same barrenness was 
believed to characterize the next Ohio stratum, the Clevelaiv' 
shale. Before the appearance of Dr. Newberry's Monograph, 
a few fossils had come to light which indicated the latent 
treasures of this unpromising horizon. Two or three spines 
of Ctenacanthus, a few cladodont teeth and one or two other 
species (see table) had been reported and were described in 
that work. Besides these, and after their discovery, a yet richer 
field was opened, when it was found that some of the great 
concretions of the shale contained not merely detached spines 
and teeth, but casts of entire fishes. Of these, one found by 
Mr. Fyler was figured and named Cladodus kepleri and the 
other found by Dr. W. Clark of Berea, was figured without 
description under the name of C. fyleri. 
Others have since been discovered — a few by Mr. Kepler — 
but by far the greater number by Dr. Clark, who has by his 
industry, skill and perseverence made this field especially his 
own. His present collection, it is hardly necessary to saw 
stands unrivalled in the world for Devonian elasmobranch s ; 
for nowhere else can be seen elasmobranch fossils of any age in 
so great numbers and in such perfection. 
Besides the above mentioned specimens, a single imperfect 
fossil found near Glasgow, Scotland and described by Dr. 
Traquair in the Geological Magazine for 1888, is the only other 
known contribution to our knowledge of the external form 
and structure of the palaeozoic elasmobranchs. His specimen 
appears also to differ cons derably from those found in Ohio 
and it is not at present easy to reconcile the descriptions/' 
•So rarely nave any fossils of the kind been found that A. S. Wooiiward 
could write in his "Catalogue" (p. 11): "The only skeletons of Carboniftrous 
fishes worthy of note are those of Sphenacanthus, Chondrenchely* and Clad- 
odus from the Lower Carboniferous of Scotland. Cladodus from the Erie 
(rather the Cleveland) shale of Ohio and Pleuracanthus from the middle Coal 
Measures of France." 
