268 



U. S. BUREAU OF FISHERIES 



Crocodilians are lonn^-lived in captivity, and so are the giant snap- 

 ping turtles (Macrochelj's) of the lower Mississippi River, which are 

 kept in the same pool with them. 



Porpoises are active day and night, but none of those brought to 

 the aquarium lived longer than two years. All mammals kept con- 

 tinuouslj^ indoors suffer for lack of pure air, as the building must be 

 heated in winter and often is densely crowded with visitors. Main- 

 taining the purity of the air at all times is difficult, and such animals 

 become tender and are liable to die suddenly of pneumonia. 



