134 PALEOZOIC FISHES OF NORTH AMERICA. 
wide without the curved point; corocoid (?) twenty-two inches long, for 
one half its length a solid subeylindrical bone three inches in diameter, the 
other haif fan-shaped and thinner. The mandibles are nearly three feet in 
length, the posterior end smooth, thin, spatulate,and curved downward, the 
anterior end gently curved upward, narrowed to an obtuse, gouge-like point 
and excavated in a deep furrow, of which the external margin is the higher 
and thinner; on the inside the margin is thicker and rounded. 
Portions of the mandibles of this species were found some years since 
by Mr. Jay Terrell in the Cleveland shale on French Creek, in Lorain 
County, Ohio, but their nature was not recognized until explained by the 
discovery of two crania, with mandibles and many other bones, by Dr. 
William Clark in the Cleveland shale on the banks of Rocky River, near 
his place of residence, Berea, Ohio. 
With commendable enthusiasm and industry Dr. Clark has followed 
up his first discovery by others, until he has now gathered a magnificent and 
unique collection of the remains of the great fish which has been named in 
his honor. 
Among the mandibles of 7. Clarkii found at Berea and on French 
Creek, Lorain County, Ohio, are some noticeable differences. Those 
obtained in the valley of Rocky River by Dr. Clark are represented some- 
what restored in Plate II, Figs. 3,4. They are nearly three feet in length, 
the posterior spatulate end about six inches wide and about three-quarters 
of an inch thick in the middle. A nearly complete mandible obtained by 
Mr. Terrell in Lorain County is about two and one-half feet long and much 
lighter, the posterior end being very thin. Another mandible from French 
Creek, of which the posterior half is complete, the anterior portion imperfect, 
is very much heavier. Compared with the other from the same locality 
mentioned above, and which has nearly the same linear dimensions, this is 
fully twice as thick and strong. These differences may be individual, sex- 
ual, or specific; the accumulation of more material will doubtless decide 
which, but meantime I have thought it best to notice them. 
In comparing the bones of the two species of Titanichthys here described 
the differences in the mandibles will strike the most casual observer, and 
will perhaps suggest the question whether the two forms are generically 
