FISHES 



89 



" saws " are among the common objects seen in museums, or 

 brought home by sailors. Powerful side -strokes can be given 



Fig. 369. Saw-Fish (Pristis antiquorum] 



with these formidable weapons, which in extreme cases may be 

 6 feet long. 



Crushing Teeth. Some sharks present a parallel to the 

 arrangements already described for Wrasses and Wolf -Fishes, 

 their teeth having broad crushing crowns adapted for breaking 

 the hard investments of various invertebrates. An example is 

 furnished by the Port Jackson Shark (Cestracion Philippi] 



Fig- 370. Port Jackson Shark (Cestracion Philippi) 



(fig. 37)> which feeds upon molluscs, and in which the mouth 

 is placed at the front end of the head, a more convenient place 

 than is usual among sharks. In this fish the front teeth are small 

 and pointed, while the remainder are adapted for crushing. 



Rays and Skates (see vol. i, p. 289) are bottom-fishes, inca- 

 pable of swimming with the rapidity characteristic of typical sharks. 

 They therefore, as might be expected, feed chiefly upon inver- 

 tebrates, in accordance with which their numerous rows of closely- 

 packed teeth are small in size. In such cases as the Eagle- 

 Ray (Myliobatis aquila) (fig. 371) the teeth are broadened out 



