54! 



The True Sharks 



The dorsals are small and far back, the tail is slender with 

 small fins, all these being characters shared by the rays. But 

 one genus is now extant, widely diffused in warm seas. The 

 species if really distinct are al! very close to the European 

 Sqnatina squatina. This is a moderate-sized shark of sluggish 

 liabit feeding on crabs and shells, which it crushes with its 

 small, pointed, nail-shaped teeth. Ntimerous fossil species of 

 Sqnatina are found from the Triassic and Cretaceous, Sqnatina 

 alifera being the best known. 



Family Pristiophoridae, or Sawsharks. — Another highly aber- 

 rant family is that of the sawsharks, Pristiophoridcc. These are 

 small sharks, much like the Dalatiida in appearance, but with the 

 snout produced into a long flat blade, on either side of which is a 



Fig. 341 — Sawshark, Fr/s^iop/iorws /opomais Giinther. Specimen from Nagasaki. 



row of rather small sharp enameled teeth. These teeth are smaller 

 and sharper than in the sawfish (Pristis) , and the whole animal 

 is much smaller than its analogue among the rays. This saw 

 must be an effective weapon among the schools of herring and 

 anchovies on which the sawsharks feed. The true teeth are 

 small, sharp, and close-set. The few species of sawsharks 

 are marine, inhabiting the shores of eastern Asia and Aus- 

 tralia. PristiopJiorus japoiiicus is found rather sparsely along 

 the shores of Japan. The vertebra? in this group are also tecto- 

 spondylous. Both the Sqnati)ia and Pristiophorns represent a 

 perfect transition from the sharks and rays. We regard them 

 as sharks only because the gill-openings are on the side, not 



