U4 Tin American Geologist. August, 1893 
Love of the work is rarer still and without this no one, what- 
ever may be hi 8 gifts, can possibly succeed. The reward, in 
this money-making age, does not attract many votaries. Pure 
science is, like virtue, herown and her only reward. But the 
world is the better and men are the wiser for the Labors of 
such men in fields of great difficulty and intricacy. Let us 
hope that ere long - others will come out and join those who 
now are at the task and share with them "the burden and the 
heat of the day." 
Returning from this brief digression, we desire here to 
dwell for a time, for the benefit of the many readers of the 
Geologist who do not pretend to special knowledge and whose 
pleasure and profit the Magazine is, in part at least, intended 
to serve, on the characters of those species which, so far as 
we yet know, must have been the rulers — the tyrants if the 
reader so please — of the muddy waters wherein the Cleveland 
Shale was deposited. So little is yet known of them that it is 
impossible to write of more than the foreparts of their bodies 
as their latter ends have never been discovered. So to make 
the comparison equal for all, we will consider only the jaws 
and principally the lower jaw, or the mandible, as it is usually 
called. 
The earliest known was a species of Dinichthys different 
from D. Hertzeri of the Huron Shale. Of this creature the 
lower jaws are the parts commonly found and the best pre- 
served. They have been so well studied, described and fig- 
ured by Newberry that little remains to be known about them 
and the specimens now reconstructed in the museum of 
Columbia college, New York, "the pride of that collection," 
are the admiration and, if it were possible, the envy of ich- 
thyologists the world over. 
The jaw of Dinichthys is a deep but not thick blade, thin- 
ning out behind where it was inserted into a mass of muscle 
or ended in cartilage. Anteriorly it grew thicker and termi- 
nated in a strong and nearly vertical, pointed tooth with very 
massive l>ase, whose point fitted, as shown by the wear, on the 
inner and anterior face of its antagonist above. 
Behind this tooth is a short depression in the jaw followed 
by a long, sharp-edged cutting blade without teeth and al- 
ways worn on the outer face from continual shearing contact 
