CLASS GANOIDEI. 



FIG. 159. 



Lepidos'teus 6s' se us. Gar-pike. ^.Fulcrum. (|.) 



fishes. The air-bladder is connected by means of a tube 

 with the oesophagus, and is used as a lung.* 



ORDER HALECOMORPHI (ha le ko mor'fl). 



The Mud-fish, found in our lakes and rivers from 



Minnesota to the Mexican Gulf, is the highest Ganoid, 



and the one most resembling the members of the fol- 



FIG. 160. 



A ml' a cat' va. Mud-fish. 



lowing class. In confinement, this animal has been ob- 

 served to come regularly to the surface of the water 

 for fresh air, using its air-bladder, as does the Gar, for a 

 lung.f 



* The air-bladder of higher forms is a sac, containing gas, and is of use in 

 changing the specific gravity of the fish. 



t Dr. B. GK Wilder says essentially, " one came to the surface at intervals to 

 discharge a bubble of air. Held about six inches below the surface, it still 

 emitted a large bubble. After a second or two of quiet, it escaped from the 

 hand, and apparently gulped in a large quantity of air, and descending, remained 

 quiet the usual interval." 



