Suborder Heterosomata 



4 8 7 



of its allies, would be the most primitive of the group. If it be 

 so, the simpler structure of the halibut and its relatives is due 

 to degeneration, which is probable, although their structure has 

 the suggestion of primitive simplicity, especially in the greater 

 approach to symmetry in the head and the symmetry in the 

 insertion of the ventral fins. 



Soles have been found in the later Tertiary rocks. Solea 

 kirchbergiana of the Miocene is not very different from species 



FIG. 434. Window-pane, Lophopsefta maculata. Virginia. 



now extant in southern Europe. No remains referable to 

 allies of the halibut or plaice are found in Tertiary rocks, and 

 these relatively simple types must be regarded as of recent origin. 



The Turbot Tribe : Bothinae. The turbot tribe have the mouth 

 large, the eyes and color on the left side, and the ventral 

 fins unlike, that of the left side being extended along the ridge 

 of the abdomen. The species are found in the warm seas only. 

 They are deeper in body than the halibut and plaice, and some 

 of them are the smallest of all flounders. It is probable that 

 these approach most nearly of existing flounders to the original 

 ancestors of the group. 



Perhaps the most primitive genus is Bothus, species of 

 which genus are found in Italian Miocene. The European 



