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cranium, and the lower or rig-lit 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 

 nia)^ be parallel or even convergent, while after death they 

 are Avidely 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 svirface 

 uppermost the right orbit looks downwards and slightly 

 laterally. 



The interorbital septum is formed by the right 



