CHAPTER XXVII 
SUBORDER HETEROSOMATA 
FIHE 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 
(€repos, differing; cGua, 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 1s 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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