1894.] TELEOSTEAK MORPHOLOGY. 443 



proximal parts of the two oblique muscles, which are, as usual, 

 attached to the posterior face of the expanded front part of the left 

 ectethmoid ; these muscles are seen to pass to the eye to which 

 they belong by dipping under the pseudomesial process. 



On turning the specimen over and laying bare the left side of 

 the skull, it is found to have the appearance shown in Plate XXX. 

 fig. 9 ; a figure of the skull of a normal Sole (fig. 10) is added for 

 purposes of comparison. 



Below the pseudomesial is seen in either specimen a tolerably 

 large foramen, which is considerably largest, however, in the 

 abnormal fish. It would appear from Mr. Cunningham's figure 

 (op. cit. pi. xi. fig. 6) that it may be much smaller in normal Soles 

 than in the specimen from which my drawing was made, but the 

 bones of Teleosteans are notoriously variable. This foramen in 

 normal Flat-fish, as we have seen in the second part of this paper, 

 puts the left accessory visual organ into connection with the left 

 orbital cavity and gives exit to a cranial nerve. 



In the specimen before us, however, the whole of the left orbital 

 apparatus protrudes through this foramen, the left accessory 

 visual organ being rather backwardly displaced. It was not very 

 well preserved, and I did not ascertain the position of its opening 

 into the orbital cavity, but this appeared to be external to the 

 skull. The eye itself is resting internally against the left 

 ectethmoid and the anterior part of the pseudomesial. The length 

 of the oblique muscles does not allow it any outward displacement, 

 and the width of the foramen is not sufficient to allow it to be 

 drawn inwards. The recti muscles pass to their usual place of 

 insertion on the inner face of the parasphenoid, and the optic nerve 

 to its origin on the ventral face of the brain. 



Comparing the normal and abnormal skulls from the left side we 

 find only two points of difference, viz. (a) the foramen is largest in 

 the abnormal example, (b) the left ectethmoid is less developed and 

 lacks the usual antero-dorsal prominence in the abnormal example. 



That the left ectethmoid has nevertheless undergone the usual 

 rotation is shown by the position of the insertions of the oblique 

 muscles. We have already noticed from the outside that the eye 

 is partially withdrawn from the surface. Internally its connection 

 with the skin is very slight, in fact it is difficult to avoid separating 

 the outer from the inner layer of the cornea in making the necessary 

 observations. The mandibulary branch of the V-cranial, passing 

 directly below the eye-muscles, appears in some degree to restrict 

 the eye to the position it now occupies. 



To recapitulate, we have before us a specimen in which there 

 has been practically no migration of the left eye, and yet in which 

 the skull presents, save for a slight deficiency in the left ectethmoid, 

 all the characters which one finds in a specimen in which the usual 

 migration has taken place. The rotation of the mouth-apparatus 

 is quite normal, but I have omitted to consider this because, as 

 Cunningham truly remarks, it is a feature entirely independent of 

 that of the orbital part of the skull. 



