ARTICLE VI. 
DESCRIPTIONS OF THE REMAINS OF FISHES FROM THE CARBONIFEROUS 
LIMESTONE OF ILLINOIS AND MISSOURI. 
BY JOSEPH LEIDY, M. D. 
[Read July 18, 1856.] 
The present communication consists of short descriptions of remains of Cestraciont fishes, 
principally discovered by Dr. Benjamin Shumard of St. Louis, in the Carboniferous Lime- 
stone of Ilinois. 
From the variety in form of the teeth in different positions of the jaws of Cestracion 
Phillippii, the only surviving member of its family, we may infer that in the determi- 
nation of extinct species from isolated teeth, which form the usual condition of the remains 
of Cestraciontes, we may consider as characteristic of several genera and species what 
may really belong to a single species. Under the circumstances the error is perhaps un- 
avoidable; and it must be left to subsequent discovery, in which entire series of teeth in 
their original relationship may be found, to correct the error. 
COCHLIODUS AG. 
1. Cocutiopus nitipus, Leidy. 
This species is proposed on the specimen of a tooth, apparently from the left side of 
the lower jaw. The tooth is trilateral in outline, with the inner border convex, the an- 
terior thick and straight, and that postero-externally straight and oblique in its direction. 
The triturating surface is transversely convex, with an anterior narrower and a posterior 
broad groove dividing three ridges crossing the tooth obliquely. Structure finely porous. 
Length from the posterior to the anterior angle seven lines; breadth of anterior border 
four and a half lines; breadth of inner border six lines. 
Locality.—Carboniferous limestone of Chester, Illinois. Plate V., Fig. 2. Tooth of 
“Cochliodus nitidus. 
