TELEOSTS. 



265 



the head. In early life they are sym- 

 metrical : but very soon, in some spe- 



efore reaching the length of an 

 inch, they turn over upon one side, 

 and the eye of the lower surface grad- 

 ually works around to the upper side, 

 twisting the bones of the skull in its 



_;e. The group is nearest the 

 gadoids, and probably these have both 

 descended from some common ances- 

 tor. Many of the species are valuable 

 as food. All are bottom feeders, and 

 some come from the deeper seas. 

 PLEURONECTID.-E, preopercular mar- 

 gin distinct; mouth large or moderate. 

 Hippoglossus, halibut of northern 

 seas ; Paralichthys ; Pseudopleuro- 

 nectcs. winter flounders; Pleuronectes, 

 plaice ; Lophopsetta, window pane. 

 P sett a (Rhombus}, turbot (dates from 

 the eocene). SOLEID.E, preopercular 

 covered by skin and scales in front; 

 mouth small and twisted. Achinis. 

 American soles ; Solca (dating from 

 the oligocene), European sole. FIG. 265. Cranium of a plaice 



(Platessa}, from Huxley, showing the 



distortion of the bones ; the dotted line, ab, being the middle line. EpO, epiotics; 

 />, frontals; Eth, ethmoid; Pa, parietal; Prf, prefrontal; SO, supraoccipital; 



>sition of eyes. 



FIG. 266. Winter 

 flounder, Pseudopleu- 

 ronectcs americanus, 

 after Goode. 



SUB-ORDER 22. HAPLODOCI. 



('/ill arches reduced to three : head large ; post-temporal undivided ; 

 dorsal fins two, the dorsals, pectorals, and ventrals spined in front, the 



