CHAPTER XXVII 

 SUBORDER HETEROSOMATA 



HE Flatfishes. Perhaps the most remarkable offshoot 

 from the order of spiny-rayed fishes is the great group 

 of flounders and soles, called by Bonaparte Heterosomata 

 (erepos, differing; crcSyuo', body). The essential character of this 

 group is found in the twisting of the anterior part of the cra- 

 nium, an arrangement which brings both eyes on the same side 

 of the head. This is accompanied by a great compression of the 

 body, as a result of which the flounders swim horizontally or 

 lie flat on the sand. On the side which is uppermost both eyes 

 are placed, this side being colored, brown or gray or mottled. 

 The lower side is usually plain white. In certain genera the right 

 side is uppermost, in others the left. In a very few, confined 

 to the coast of California, the eyes are on the right or left side 

 indifferently. 



The process of the twisting of the head has been already 

 described (see p. 174, Vol. I). The very young have the body 

 translucent and symmetrical, standing upright in the water. 

 Soon the tendency to rest on the bottom sets in, the body 

 leans to left or right, and the lower eye gradually traverses the 

 front of the head to the other side. This movement is best 

 seen in the species of Platophrys, in which the final arrangement 

 of the eyes is a highly specialized one. 



In some or all of the soles it is perhaps true that the eye 

 turns over and pierces the cranium instead of passing across 

 it. This opinion needs verification, and the process should be 

 studied in detail in as many species as possible. The present 

 writer has seen it in species of Platophrys only, the same genus 

 in which it was carefully studied by Dr. Carlo F. Emery of 

 Bologna. In the halibut, and in the more primitive flounders 



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