FISHES OF THE CARBONIFEROUS SYSTEM. 153 
proportions of that of the larger species, had this peculiarity, that the pos- 
terior end of the cutting edge carried denticles. At first sight these resemble 
those on the mandibles of D. Hertzeri, but when examined they are seen to 
be compressed and to be only strong serrations, which could have had little 
functional importance. This character seems to be an inheritance from the 
older species of the genus, D. Hertzeri, in which both the mandibles and 
maxillaries are set with conical pointed teeth, and thus it is a kind of con- 
necting link between that form of dentition and the cutting edges of the 
mandibles and maxillaries of D. Terrelli, ete. 
It is not true, however, that all the earlier species of Dinichthys had 
pointed teeth on the mandibles and maxillaries and all the later ones cut- 
ting edges, for Prof. J. M. Clarke has described in the Bulletin of the U. 8. 
Geological Survey, No. 16, page 17, the mandibles and maxillaries of a species 
of Dinichthys which he calls D. Newberryi. They are about the size of 
those of D. intermedius, and have cutting edges precisely as in D. Terrelli. 
‘These specimens were found in the Hamilton shales of western New York, 
the geological equivalents of the Huron shale of Ohio. Hence D. Hertzeri 
and D. Newberryi were contemporaries, and the two styles of dentition were 
in use at the same time. The dentition of D. intermedius does not therefore 
represent a phase of progressive transition from one form to the other, char- 
acteristic of an intermediate period, but is rather a kind of hybrid between 
the two older forms. 
After the discovery of the first mandible with the characters mentioned 
above a number of others were obtained, all of about the same size and 
having the compressed denticles at the back end of the cutting edge. I 
have therefore been led to accept the suggestion first made by Mr. Terrell, 
that these represent a distinct species, and I have given it a name indicative 
of the intermediate position it holds between the larger and smaller forms of 
Dinichthys found in the Cleveland shale and also in the denticulation of the 
mandibles between them and D. Hertzeri of the Huron shale. It should 
also be mentioned as confirmatory of this view that these smaller mandibles. 
are as much worn by use as any of the larger ones; from which we may 
infer that they belonged to mature individuals. I may add that in the 
Cleveland shale at Brooklyn, Cuyahoga County, Ohio, while the remains 
