THE ORIGIN OF MAN 69 



rine in their habits and preyed upon fishes. Their 

 limbs were converted into swimming paddles, and 

 there was a dorsal fin and a large tail-fin, the lat- 

 ter being the principal organ of propulsion. The 

 muzzle was drawn out into an elongated slender 

 snout, armed with numerous teeth, which were 

 set in a continuous groove, instead of in separate 

 sockets. The neck was short and the skin very 

 smooth. Another group of carnivorous reptiles 

 was that of the Plesiosauria ( Greek for near- liz- 

 ard) which appeared in the Triassic and cul- 

 minated in the Jurassic and which formed a 

 curious contrast to the ichthyosaurs. The heads 

 of these were very small and the jaws were pro- 

 vided with large, sharp teeth, set in distinct sock- 

 ets. The neck was exceedingly long, slender, 

 and serpent-like, and was marked off distinctly 

 from the small, box-like body. The swimming 

 paddles were much larger than in the ichthyo- 

 saurs and probably had more to do with locomo- 

 tion. Of all the Paleozoic fishes all were absent 



