393 MANUAL OF ZOOLOGY sect. 



left side. The under side is usually pure white, the upper 

 dark. The eyes are both on the upper side, and the skull 

 is distorted so as to adapt the orbits to this change of 

 position. 1 



Fig. 237. — Pleuronectes cynoglossus (craig-fluke), from the right side. d. f, 

 dorsal fin; / e, left eye; pet. /, pectoral fin; pv. f } pelvic fin; r. e, right eye; 

 v./, ventral fin. (After Cuvier.) 



In many Teleostei, such as the eels, the skin is devoid 

 of hard parts ; but in most cases there is an exoskeleton 

 developed in the derm. In the majority this takes the form 

 of scales, rounded plates of bone embedded in pouches of 

 the derm, and overlapping one another from behind for- 

 wards. When the free border of the scales presents an 

 even curve, they are called cycloid scales ; when the free 

 edge is produced into small spines, they are distinguished 

 as ctenoid scales (Fig. 238). In exceptional cases the scales 

 may be so large and strong as to form a rigid armour. 



1 Our common flounders are Paralichthys dentatus from the southern 

 coast of New England, and Pscurfoplcuronectcs americanus from the coast 

 north of Cape Cod. 



