DAVIS: FISH-REMAINS IN THE COAL-MEASURES. 
51 
tion of the cannel coal. They were possessed of an air- 
bladder, the remains of which is preserved in a fossil state. 
It has been described as osseous ;* but after careful microsco- 
pical examination, no trace of osseous structure could be 
detected. The appearance is more nearly allied to chitine, 
but the want of good fossil examples of that substance for 
comparison leaves the question in a state of uncertainty. 
There can be little doubt, however, that the swim-bladder of 
the Ccelacanthus did serve a similar purpose to that of the 
Lepidosiren, Ceratodus, or the Sirenoid fish of the Amazon ; 
and it is not probable that bony walls would assist it in the 
performance of this function, but rather retard the operation. 
In the foregoing remarks an attempt has been made to 
show that fish may serve to indicate to a great extent the 
method of deposition of many of the varied beds which go 
to form the coal measures. In the case particularly cited, 
there is not only the evidence of the fish themselves, but also 
the coal and its immediately contiguous beds afford strong 
presumptive evidence that it was deposited in a semi- stagnant 
series of pools or small lakes, into which the vegetable 
matter was carried, whose decayed remains form the cannel 
coal, and when mixed with the mud also brought down with 
the vegetable matter, the " hubb." In the coal, as well as the 
" hubb/' large numbers of Ccelacanths have been discovered ; 
and along with these, though comparatively rare in 
comparison, are found the remains of Ganoids and 
Elasmobranchs. I have endeavoured to show that it requires 
no great stretch of scientific evidence to suppose that the 
Granoids were fresh-water fish, as they mainly are at the 
present time ; and that it is within the range of possibility 
that the sharks, during the Carboniferous Period, may have 
* Mantell's " Petrifactions and their Teachings;' 1851, p. 437. Prof. W. 0. 
Williamson " On the Microscopical Structure of the Scale and Dermal Teeth of 
some Ganoid and Placoid Fishes ," Phil. Trans, for 1849. 
