154 ROY L. MOODIE 
cially in the brain of Rhadinichthys. The remainder of the pos- 
terior portion of the brain is obscured on the two or three speci- 
mens which are available for study. The hypothalamus does 
not differ essentially from that of the smaller brains. 
VII. THE ANATOMY OF THE EAR OF THE COAL MEASURES FISH 
On either side of the posterior portion of the brain of several 
specimens of both the Coal Measures and Mississippian fishes 
there occur the vertical semicircular canals as tortuous vessels 
which are strongly bent inward in the region of the tuberculum 
acusticum (figs. 10 and 15). In size the canals seem a little 
large but this may be due to the increase owing to the segrega- 
tion and crystallization of the mineral substance composing the 
fossil. This structure has been fully described by Doctor Parker 
(08) in the Mississippian fish and his discussion is referred to 
on a previous page. : 
The ear is very completely preserved in one specimen (fig. 10) 
and the parts of the ear in other specimens are sufficiently well 
preserved so that it has been possible to reconstruct the complete, 
or at least approximately complete, anatomy of the semicircular 
canals in their relationship to each other (fig. 11). The inner 
ear is well represented in figures 15 and 16, where may be seen 
the sacculus, the utriculus, and the horizontal semicircular canal 
with its ampulla, which is rather extraordinary in the enormous 
expansion of its anterior parts. 
The ear as a whole is very unusual and is totally unlike any- 
thing I have seen figured in the literature. The chief differences 
being the unusually enlarged portions of the ampullae. In its 
gereral configuration the relation of the canals to each other is 
about as figured for other fishes, notably Acipenser as figured by 
Retzius. The horizontal semicircular canal is well shown in fig- 
ures 4, 15 and 16 and needs no further description. The form of 
this canal is quite constant and I have seen it in six different 
specimens. The ampulla of this canal is very unusual and a . 
portion of it, which has become unusually enlarged, has been 
labeled sinus (fig. 16), with no thought that this has anything 
