136 PALEOZOIC FISHES OF NORTH AMERICA. 
ous in D. Hertzert, of the Huron shale—the first species found—are repre- 
sented by a few compressed teeth at the posterior ends of the cutting edges, 
which in this, as in all the later species, constitute the effective element in 
the dentition. These and other new species are described in this memoir, 
and therefore no further reference to them is needed here. I have also 
referred elsewhere to the discovery of the bony eye-capsules of D. Terrelli, 
as well as to the pair of plates which apparently protected the arched space 
between the mandibles (Pl. VI, Figs. 1, 1°). . 
The opening of a new locality rich in fossil fishes in the valley of the 
Cuyahoga and the suburbs of Cleveland has resulted in the discovery of 
material which has afforded valuable information in regard to the structure 
of Dinichthys, and has compelled the correction of some errors in my former 
descriptions. Among the fossils collected at this point by. Dr. William 
Clark are several heads of Dinichthys intermedius, which show the structure 
with more completeness than any specimens before obtained. In most of 
the erania of Dinichthys obtained in Lorain County by Mr. Terrell the 
plates composing the cranium are so firmly united that their number, forms, 
and relations could hardly be made out. Those found in the new locality 
give us views of both the interior and exterior surfaces, where we can trace 
all the component parts. Some of these specimens are represented on Pls. 
LI and LIT, and the points of structure now reported are there more or less 
distinctly visible. The most important contribution made by these speci- 
mens to our knowledge of the head of Dinichthys is shown in the outside 
view of the entire cranium of D. intermedius, Pl. L1; where the suborbital 
plates, here in position, are seen to be the bones which we have hereto- 
fore considered as the posterior lateral plates of the plastron. Inside and 
outside views of one of those bones are given on Pl. XLVI, Figs. 1, 1% 
This species, which is much smaller than D. Terrel/li, has the suborbital 
plates relatively very short. The position of the pair disinterred in the find 
made by Mr. Terrell, which furnished the originals of the life-size figures on 
the charts that accompany volume 2 of the Palzeontology of Ohio, was such, 
that they were naturally referred to the plastron and were grouped with the 
central sternum-like plate and the two anterior lateral plates, which certainly 
belonged to the ventral armor. The later discoveries render it probable 
