GANOIDEI. 



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fishes. The endoskeleton is only partially converted into bone, 

 and the exoskeleton, by way of compensation, consists of 

 ganoid plates. The swim-bladder is destitute of an air-duct. 



This sub-order comprises the living Pipe-fishes (Syngna- 

 thidtz) and Sea-horses (Hippocampida). A few fossil forms are 

 known, dating from the Eocene Tertiary. 



Fig. ^-i.Platax altissimus, a Chzetodont from the Eocene Tertiary of Monte Bolca. 



ORDER II. GANOIDEI. The order of the true Ganoid 

 Fishes may be defined by the following characters. The endo- 



