Devonian Era in Ohio Basin. — Claypole. 347 
By the use of Dr. Clark's collection and a careful com- 
parison of the specimens the writer has been able to define more 
or less completely, several species of Cladodus, a detailed ac- 
count of which will be found beyond. 
Most of the fossils found by Dr. Clark and Mr. Kepler are 
obviously of the cladodont type of dentition. They vary how- 
ever, in details and especially in external form. Some of them 
differ considerably from either of the forms described by Dr. 
Newberry and it is uncertain if full knowledge when attainable 
will allow the retention of all the species in the old genus Cla- 
dodus. Indeed, even on the evidence of the dentition, the 
writer has found it desirable to separate two of them under a 
distinctive name — Mono cladodus. But so long as the peculiar 
dentition, as originally defined by Agassiz, is the only limit, 
it seems unadvisable to multiply generic terms. Descriptions 
are at present so meagre, with the exception of those of the 
specimens from the Cleveland shale, that it is not possible to 
determine whether or not the species on both sides of the At- 
lantic are congeneric. 
Leaving this question for the decision of the future, the 
fossds of Dr. Clark still enable us to lay down the following 
data regarding the genus Cladodus. 
Cladodus, Agassiz. 
Fish, so far as known, of moderate or large size, varying from' two 
or three feet up to fifteen or twenty feet in length. Body slender, elon- 
gated, the greatest breadth being just behind the pectoral fins and taper- 
ing off slowly toward the tail. 
Head about one-eighth or one-sixth of the total length, sometimes 
widening regnlarly from the snout to the front edge of the pectoral 
fins and, at others, attaining its greatest breadth at or near the hinder 
end of the jaws and then narrowing again a little to the fins. 
Snout blunt when seen from below; (no lateral view is known, but 
it was probably more acute) showing large olfactory cavities; eyes large, 
lateral and very near the front (anterior) part, surrounded with a ring 
of small orbital plates often well preserved. 
Mouth nearly terminal, mandibles straight, mamillaries nearly 
straight. Both are set with ten or more files of cladodont teeth on each 
side having from seven to ten teeth in every file "or about 400 in all. 
In some species, if not in all, there was a symphysial file of smaller 
teeth. The mamillaries apparently closed outside the mandibles, the two 
articulating with a well marked condyle, lint no evidence oi intermedi- 
ate suspensorium is visible. Behind the condyle is a well marked back- 
ward projecting process. Along the upper edge of the mandible is a 
