LIST OF ILLUSTRATIONS 



xv 



Jaws of Thornback, 



Common Skate and Marbled Electric Ray, 

 Teeth of Lobe-Finned Shark, 

 Restoration of Fold- Finned Shark, 

 Restoration of Spine-Finned Shark, 



PAGE 



541 



542 

 546 

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 547 



THE LOWEST VERTEBRATES AND THEIR ALLIES 



A Cartilaginous Sea-Squirt (Phallusia), 

 Pear-Shaped Ascidian (Hijpobythius), 

 A Creeping Ascidian (Clavelina), . 

 An Incrusting Ascidian (Botrylloides), 

 A Compound Ascidian (Amarucium), 

 An Individual of a Chain-Salpa, . 

 Botryllus, .... 

 Young Balanoglossus, 

 A Pyrosoma Colony, 



PAGE 



565 

 566 

 567 

 568 

 568 

 570' 

 572 

 573 

 576 



