FISHES OF THE CARBONIFEROUS SYSTEM. 199 
Ireland, and which were named by Agassiz, Labodus, Copodus, Characodus, 
etc. Similar teeth occur in the Chester and Saint Louis limestones in IIli- 
nois and Missouri, and some of these have been described by St. John and 
Worthen as species of Copodus. All of these consist of oval, rounded, or 
quadrangular dental plates of small size, arched form, and polished, pitted, 
enamel surface. Since there is no evidence of co-adaptation with other teeth 
at the sides, it has been thought that they formed a single series of three or 
more, which were placed in the central part of the mouth above and below 
and had the functions of the teeth of Atobatis, Myliobatis, ete. 
The teeth belonging to this group were named but never described by 
Agassiz. His work has been supplemented by Morris, McCoy, and J. W. 
Davis, who have endeavored to perpetuate Agassiz’s names and classifica- 
tion. Without more material in our hands it would be presumptuous to 
attempt a review of the work of those who have endeavored to distribute 
these peculiar fish teeth into generic groups, as it is evident that the dis- 
iinctions between Agassiz’s genera are not strongly marked. It is impossi- 
ble for us with certainty to refer the specimens we find to one or another 
of several genera, and if we may judge from the illustrations given by Mr. 
J. W. Davis in his Fossil Fishes of the Carboniferous Limestone, it would 
seem that some of these genera should be united. I am strengthened in this 
conclusion by an examination made some years ago, through the courtesy 
of Professor Agassiz, of the large collection of fish remains which he had 
brought to this country from Armagh. These were generally named by 
him, and of some of his species specimens are before me as I write. Among 
these is a fish tooth which bears the name of Characodus. ‘This is so like 
the one now figured that I must think them generically identical; but the 
genus Characodus, Ag., as defined and illustrated by Mr. Davis, is consider- 
ably different, the teeth being much longer transversely and with salient 
cornua. If we are to consider Mr. Davis’s descriptions and illustrations as 
an authoritative supplement to Agassiz’s work, then the tooth now figured 
should rather be considered a species of Labodus. So, for want of good evi- 
dence to the contrary, I place it there provisionally, but record its differences 
from any other known species by giving it the name marginatus; the crown 
surface being bordered on three sides by a distinct marginal band. 
