206 PALEOZOIC FISHES OF NORTH AMERICA. 
In size, form, and markings this tooth corresponds closely with some of 
the specimens of Orodus ramosus, Ag., of which species a good representa- 
tion may be seen in the geological collection of the School of Mines, Colum- 
bia College, and there can be no reasonable doubt of their specific identity. 
It is probable also that the tooth described and figured in the Geological 
Survey of Illinois, volume 2, under the name of Orodus multicarinatus, will 
prove to belong to the same species. This specimen is only a fragment, a 
part of the central cone of a tooth which must have been twice as large as 
that now figured, or any tooth of O. ramosus before known, and the surface 
bears a larger number of carinze than have been seen on the central part of 
the crown of a tooth of that species; but these differences are rather of degree 
than of kind. The peculiar ornamentation of the species is repeated, and 
we can say without hesitation that if not the same it is closely allied to that 
of the Old World. All the specimens referred to are found at about the 
same geological level; that figured in the Illinois report was from the Goni- 
atite limestone, the base of the Lower Carboniferous at Rockford, Ind. 
The foreign specimens came from the Mountain limestone, and that now 
under examination from the Waverly sandstone at Grindstone City, Mich. 
Mr. J. W. Davis has recently published in his paper, ‘The Fossil 
Fishes of the Carboniferous Limestone,”! better illustrations of the teeth of 
Orodus ramosus than any before given, and has shown that they exhibit as 
great differences among themselves as they do from the teeth with which I 
have compared them. 
ACONDYLACANTHUS OCCIDENTALIS, N. & W. 
Plate XXV, Fig. 6. 
The spines to which this name has been given are from the Saint Louis 
limestone. They are from eight to twelve inches in length, relatively slen- 
der, gently arched backward; sides flat or arched; anterior edge sharp; pos- 
terior edge deeply furrowed, and bordered by two rows of small, acute, 
compressed and depressed hooks. The lateral surfaces are occupied by 
numerous subequal, parallel, continuous, smooth, fattened cost; near the 
base about fifteen, in the middle twelve, and within an inch of the summit 
1Trans. Dublin Royal Society, 2d series, vol. 1, p. 391, pl. 50. 
