TELEOSTS. 



26$ 



the head. In early life they are sym- 

 metrical ; but very soon, in some spe- 

 cies before 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 

 passage. 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- 

 nectes, winter flounders ; Pleuronectes, 

 plaice ; Lophopsetta, window pane. 

 Psetta {Rhombus}, turbot (dates from 

 the eocene). SOLEID/E, preopercular 

 covered by skin and scales in front ; 

 mouth small and twisted. Achirus, 

 American soles ; Solea (dating from 

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



(Platessa), from Huxley, showing the 



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

 Fr, frontals; Eth, ethmoid; Pa, parietal; Prf, prefrontal; SO, supraoccipital;, 

 Cr, position of eyes. 



FIG. 266. Winter 

 flounder, Pseudopleu- 

 ronectes americanus, 

 after Goode. 



SUB-ORDER 22. 



HAPLODOCI. 



Gill arches reduced to three ; head large ; post-temporal undivided ; 

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



