A FISH BRAIN FROM THE COAL MEASURES 147 
nodules split when struck with the hammer. The stone sur- 
rounding the fossil is relatively soft and may easily be worked 
with a sharp tool (fig. 5). In this way were exposed the struc- 
tures shown in figures 15, 16 and 17. 
There are a dozen or more nodules which exhibit the brain in 
varying degrees of perfectness. The two figured (figs. 15-17) are 
the best preserved and they are the ones which first called at- 
tention to the possibility of their neural nature. The following 
description is based in large part on these specimens. Among 
the brains in my possession there are two which present charac- 
ters at variance with the type brains. Whether this is due to 
variation in the species or whether these characters represent 
another form I am not sure. One of the brains has become 
loosened from the nodule so that we may study its characters 
from all sides, as was noted by Eastman (’08), p. 267, fig. 40 b) 
for the brain of Rhadinichthys. Four specimens show the semi- 
circular canals beautifully. 
The brain as a whole may be best understood from an exami- 
nation of the figures (figs. 15-17). The entire length of the best 
preserved and most complete brain is 15 mm. Its height is 6 
mm. The optic lobes measure 5 mm. in median length. The 
figures were all made by Mr. Tom Jones, who carefully meas- 
ured the various parts of the brain with fine pointed calipers 
and determined the dimensions on a divided millimeter scale so 
that the proportions are correctly shown; the magnification un- 
der this system of measurement being easily determined. 
There is no modern fish so far known with a brain sufficiently 
~ comparable to the Coal Measures brain to allow a direct com- 
parison. On the advice of Professor C. Judson Herrick, to whom 
I am indebted for advice and help throughout the entire course 
_of this investigation, I have described the brain independent of 
any attempt to compare it directly with modern fishes, although 
a few references are made to the literature of modern fishes in 
cases where the several parts of the brain seem to call for such 
comment. This wide separation in structure from modern fishes 
may be due to the degree of evolution or to the environmental 
adaptation of the Coal Measures fish. It is difficult, if not im- 
