r)() 



SIlAh'KS. C.WOIDS 



and (allying away stones, wliich they seize with tlieir sucker-like niautii. 



The visitor should next insj)ect the cases of sharks which are situated 



Sharks '^^'^' ^^^^' entrance hall on the south side. These include 



various forms of sharks and rays, selected as typical 



niciiilKTs of tills ancient <!;r()up — for the sharks have numerous characters 



which j)ut tlieni in the ancestral line of all other ^Toups of true fishes. 



Xext to he visited are the silver sharks or Chiinreroids, which are 

 exhibited by the side of the lamprey case. They are now known to be 

 highly modified sharks: their scales have failed to develop, and their 

 heavy "teeth" apjx'ar to rei)resent many teeth fused toj2;ether. These 

 fishes are now very rare and occur, with few exceptions, in the deep sea. 

 The present models show the characteristic forms. 



The adjacent case (at the left) pictun^s the three types of surviving 

 lun<>;fishes, and the models are arran<2;ed to indicate the life 

 habits of these interesting forms. Thus, they are shown 

 going to the surface of the water to breathe; and their positions indicate 

 that they use their paired fins just as a salamander uses its arms and legs. 

 In fact there is reason to believe that the land-living vertebrates are 

 descended from some ancient form of lungfish. One sees in this case 

 also a 'Vocoon," in which the African lungfish passes the months when 

 the streams are dried up; it then breathes only by its lungs. 



Lungfish 



A PORTION OF THE PADDLE-FISH GROUP 



( )ne now ))asses into the north aisle of the fish galliMW and stops at the 

 first case on the left. Here appear all tyi)es of existing 

 (lanoids. These are fishes that represent, as it were, a 

 half-way station betwcnni lungfishes and sharks on the one hand, and the 



Ganoids 



