On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 387 
under the term Orodontide, the genera Orodus, Agassiz ; Lophodus, Rowanowsky ; 
and Petrodus, M'‘Coy : “parce que les dents des deux premiers de ces genres ont 
une forme générale qui les rapproche les unes des autres, et que celles du troisiéme 
ont une trés grande analogie par leur structure interne et par leur forme extérieure 
avec les dents antérieures des Cestracion.” The Orodontide is regarded by M. de 
Koninck as a group of the family Cestraciontide, but no further definition is given 
The teeth of the genera comprised in the Orodontide, which have been found in 
the Carboniferous rocks of the British Islands, are in nearly all cases quite dis- 
sociated and separated into single specimens. In a few rare instances, as in 
Pl. L., figures 1 and 3, two or three teeth are found united antero-posteriorly, but in 
no instance have teeth been discovered whose lateral extremities have been either 
united or placed in such a relative position as to exhibit the-method of arrange- 
ment transversely ; neither have they served in any way to indicate how the teeth 
were disposed on the jaws, or the number which existed in each fish. It is pro- 
bable that the circumstances attending their deposition may account for the 
separation of the teeth. The limestone, in which the specimens are found, would 
naturally be a deposit which accumulated slowly, so that the body of the fish, with 
the exception of the teeth and the spines, if they had any, being composed entirely 
of cartilage and fleshy substances, easily decayed. As the connecting tissues 
became decomposed, the teeth, released from their attachment, were disturbed and 
more or less distantly separated by the action of waves or currents, and it was only 
in rare instances that two or three teeth became embedded in the sediment with 
sufficient rapidity to secure their preservation in natural juxtaposition. It is 
fortunate that other specimens have been found in shales of the Coal Measures of 
Osage County, Kansas, in America, which are well preserved, and retain the same 
or nearly the same relative position to each other in the fossil state which they 
bore when living. The deposition of the mud forming the shales doubtless pro- 
ceeded with much greater rapidity and less disturbance than that of the limestones, 
and the result has been that the fishes became buried in the sediment before a 
sufficient time had elapsed for their decomposition and dispersion, and the hard 
parts are preserved in a more or less natural and undisturbed state. 
A consideration of the Kansas specimens throws much light on the nature and 
relationship of the Orodontide as a group. They are described by Messrs. 
St. John and Worthen, in the “ Paleontology of Illinois,” Vol. VI., p. 311, and are 
considered by the authors as a separate genus, for which they have instituted the 
name Agassizodus, in acknowledgment and recognition of the services of that 
eminent ichthyologist. The specimen (op. cit., pl. vit, figs. 1-22) consists of 
about four hundred and fifty to five hundred teeth in their natural position, and 
comprises the whole of the left ramus of what appears to be the mandible or lower 
jaw and a few teeth of the right mandible. After describing the arrangement of 
the teeth, the authors remark that the teeth present “almost precisely the same 
