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cranium, and the lower or right eye is slightly in front of 
the upper or left. The prominent interorbital ridge 
formed by the frontal is continued a little way round in 
front of each eye, that portion in front of the left being 
formed by the mesethmoid and left prefrontal, and that in 
front of the right eye by the right prefrontal. The inter- 
orbital ridge is continued backwards into the line of 
tuberosities. In the dead fish each eye lies in a little 
concavity, and the skin round it is loose and thrown into 
folds. This appearance may also be seen in the living 
fish, but it will be noticed that the eyes often project very 
markedly from the surface of the head, and that their axes 
may be parallel or even convergent, while after death they 
are widely divergent. There are no eyelids, and the 
cornea is flattened. 
The orbits.—The left orbit (fig. 1) is bounded inter- 
nally by the right frontal and an anterior process of the 
left frontal, anteriorly by the mesethmoid and left pre- 
frontal, externally by the processes of the left frontal and 
prefrontal forming the pseudomesial ridge of Traquair, 
and posteriorly by the left frontal. When the cranium is 
placed dorsal surface uppermost the left orbit looks 
upwards and to the right. The right orbit is not bounded 
completely by bony walls as is the case with the left. 
Only internally and anteriorly do the bones adjacent to it 
lie close to the skin. Those are the right frontal and 
prefrontal. The bony structures external and posterior to 
the orbit are the parasphenoid bar and the alisphenoid. 
All these bones lie nearly in one plane, and the external 
and posterior walls of the orbit are formed by strong 
muscle masses. When the cranium is held dorsal surface 
uppermost the right orbit looks downwards and slightly 
laterally. 
The interorbital septum is formed by the right 
