A FISH BRAIN FROM THE COAL MEASURES 175 
-Olfactory tract 
Olfactory 
lohe,. 4 fe ) 
-Plexiform 
— vessel 
Lateral lo 
of Ccerehell (27 
15 
circular canals. The structure labeled ampulla is the external ampulla of the 
horizontal semicircular canal, which is the one shown in the figure. The posterior 
part of the external ampulla is enlarged into a prominent portion which in figure 
16 is labeled sinus, with no thought of its being the utricular sinus. The plexi- 
form vessel may be the stalk of the epiphysis or, asis more likely, the median venous 
blood vessel. The longitudinal tubular vessels to either side of the posterior 
portions of the brain are the upper parts of the vertical semicircular canals. 
The structure labeled with a star (*) is what at first was looked upon as a pineal 
body, but it is more probably a venous sinus. 
