The Cladodotit Sharks. — Clay pole. 365 
is a proof of great skill and sagacity that he succeeded, witii 
the meager evidence afforded by so imperfect a specimen as 
must be that from East Kilbride, in constantly approximating 
to the truth at every step. This is evident when we take into 
consideration the new fossils of the Cleveland shale of Ohio. 
The several species which have already been described and 
others still awaiting examination leave no standing ground 
for the theory that (Hadodus and Ctenacanthus were identical 
or even nearly related to one another. Setting aside the 
weighty, but not determinative fact, that with one or two 
very doubtful exceptions, no specimens of Ctenacanthus have 
ever been found in the Cleveland shale in northern Ohio, we 
have the decisive evidence of the fossils themselves, for among 
all the numerous specimens of Cladodi/s that have come to 
light from this stratum of the upper Devonian, not a single 
one shows any trace of a spine on any of its fins. Several of 
these fossils are so well displayed and so well preserved that 
had fin-spines existed they could hardly have escaped detec- 
tion. The pectoral and caudal fins are very coarsely rayed 
(the former anteriorly only), but the ventrals are compara- 
tively soft. Evidence regarding the dorsal or dorsals is some- 
what less clear, but scarcely less certain, in consequence of 
the position of the fishes. 
The evidence of the fossils may therefore be regarded as 
conclusive in favor of the oi^inion that Cladodun was a 
genus of spineless sharks, at least so far as concerns the North 
American upper Devonian forms, and the specimen of Dr. 
Traquair bears testimony in the same direction for those of 
the Carboniferous strata. All connection with the si)in3' 
sharks is consequently cut ofl', and it remains to discover the 
wearers of the formidable weapons so abundant in certain 
strata. 
2. Tketh. — If the evidence of these Ohio fossils is thus 
conclusive regarding the spines of the cladodonts, that con- 
cerning their teeth is not less valuable, if less assuring. In- 
deed, some of it is decidedly unsettling of previous opinion, 
for it is more than likely that one result of the study of these 
fossils will be to destroy all confidence in the species of Clo- 
<lod>is alread}'- based on the form of the teeth. Thus far, all 
the names given rest on this basis alone. The utter uncer- 
