FISHES OF THE CARBONIFEROUS SYSTEM. Pinel 
however, are some fish remains which we must consider marine, as those of 
the Crinoidal limestone of Ohio and western Pennsylvania, and the much 
thicker and more wide-spread limestones of Coal Measure age in the Far 
West. Here we find Petalodus, Cladodus, Ctenoptychius, ete., and in Arizona 
the only Paleeozoic Pycnodonts yet found on this continent. 
There are a few localities which deserve mention from the number of 
species they have furnished. These are Linton, Ohio; Morris, Belleville, 
and Carlinville, Ill. Probably there are many others quite as rich, but they 
have not yet been discovered or properly exploited. 
The Linton locality is especially interesting and instructive. It has 
already yielded more than twenty species of fishes and nearly forty species 
of aquatic amphibians, all inhabitants of the same body of water. These 
are found in a thin stratum of cannel, which, over a limited area, underlies a 
thick bed of cubical coal (No. 6, of the Ohio Reports), of which the place 
is near the top of the Lower Coal Measures. This is a bed of coal which 
extends over some thousands of square miles, and it is usually a soft coking 
coal, not unlike that of the Pittsburgh seam, which lies about five hundred 
feet higher. At Linton, however, we have evidence that the great marsh in 
which the peat accumulated that formed Coal No.6 was for a time a lake 
or lagoon, inhabited by the fishes and amphibians to which I have referred. 
While this remained an open body of water carbonaceous mud accumulated 
at its bottom, derived from the drainage of the neighboring marsh, which 
carried with it fine particles of completely macerated vegetable tissue. In 
this carbonaceous mud, now cannel coal, were buried the scales, bones, 
spines, and often entire individuals of the inhabitants of the water above. 
Sometimes nearly the whole mass is made up of animal débris. Many of 
the fishes and amphibians were highly carnivorous and powerful, as we 
learn from their teeth and coprolites. The largest of the amphibians must 
have been eight or ten feet in length, having strong jaws, set with numerous 
lancet-shaped teeth an inch or more in length. The largest fishes were 
probably not much their inferiors in size. 
After a sufficient time had elapsed for many generations of fishes and 
aquatic salamanders to live and die the lake was filled by the extension of 
its peaty shores into it—just as so many lakelets are filled and obliterated 
