THE ORDER AMONG ANIMAL TYPES 



PISCES 



117 



F/G. 66. CyCLOSTOMATA {LAMPREY EEL) 



FIG 67. ELASMOBRANCHII (DOGFISH SHARK) 



FIG. 68. TELEOSTII {RINGED PERCH) 



Figs, dd, 67, and 68. — Representatives of three types of Pisces. Compare and 

 note the changes from the simple toward the complex in the gill clefts which in 

 the perch are covered and protected by the shield-like operculum, the fins, the 

 mouth region, and the integument. 



