LIST OF ILLUSTRATIONS 



xv 



Thornback Skates, . 

 Jaws of Thornback, 

 Common Skate and 

 Ray, 



Marbled Electric 



PAGE 



2915 

 2917 



2918 



Teeth of Lobe-Finned Shark, 

 Restoration of Fold-Finned Shark, 

 Restoration of Spine- Finned Shark, 



PAGE 

 2922 

 2923 

 2923 



THE LOWEST VERTEBRATES AND THEIR ALLIES 



PAGE 



Group of Lampreys, . . . 2928 



Hagfish, ..... 2930 



Skeleton of Primeval Lamprey, . . 2931 



Restoration of Pteraspis, . . . 2932 



Restoration of Cephalaspis, . . 2933 



Restoration of Pterichthys, . . 2933 



Lancelet, ..... 2935 



A Leathery Sea Squirt (Microcosmus), . 2938 



Section of Sea Squirt, . . . 2939 



PAGE 



A Cartilaginous Sea Squirt (Phallusia), 2941 



Pear-Shaped Ascidian (Hypobythius), . 2942 



A Creeping Ascidian (Clavelina), . 2944 



An Incrusting Ascidian (Botrylloides), . 2945 



A Compound Ascidian (Amarucium), . 2946 



An Individual of a Chain Salpa, . . 2947 



Boiryllus, ..... 2948 



Young B alano glosstiS) . . . 2951 



A Pyrosoma Colony, . . . 2954 



