CHORD ATA — VERTEBRATA — REPTILES 365 



bone \\ith a keel. The power of flight was probably bat-like, 

 more feeble than that of birds (Fig. 151). 



The Pterosauria begin suddenly, fully differentiated, in the 

 Jurassic and become extinct in the Cretaceous. They vary 

 in size from that of a sparrow to double that of an albatross. 

 The earlier forms had sharp teeth. Rhamphorhynchus (Ju- 

 rassic) had a long tail with an expanded membrane at its tip 

 indicating very rapid turnings in its flight, which, with its long, 

 sharp, slender teeth suggests that it was probably an insect 

 feeder. Pterodactylus (Jurassic) had a very short tail. Some 

 of the later forms were toothless, possibly fish-eating. Some 

 huge ones {Pteranodon) from the Kansas Cretaceous had a 

 skull over thirty inches long with a probable stretch of wings 

 of twenty feet. The largest known living sea-bird, the albatross, 

 has a stretch of wings of only twelve feet, with a weight of eight- 

 een pounds. 



Order 7, Crocodilia 



Reptiles with the dorsal surface of body, or both dorsal 

 and ventral surfaces, covered with rows of sculptured bony 

 plates which are covered with horn. Scales also present. 

 Known from the Triassic to the present. 



The Crocodilia are a modern edition of some dinosaur char- 

 acters. The genus Belodon (Triassic) may belong to a stock 

 ancestral to the Crocodilia or may possibly be assigned to the 

 early dinosaurs. Living examples are the crocodiles and 

 alligators. 



Order 8, Chelonia {Turtles, etc.) 



Reptiles with body inclosed in bony plates, — the dorsal 

 carapace and ventral plastron, composed largely of the ex- 

 panded dorsal and ventral parts of the ribs. Between these 

 plates the animal can for protection withdraw head, legs and 

 tail. These plates and often other portions of the body are 

 covered with horny expansions and scales. The jaws are with- 



