STORY "OF THE REPTILES 



'CHAPTER X 



INTJJODFCnON, DEFmmON; WHAT CAME IN WITH THB 

 EEPTILES ; OBDEES, LIMBS, TOES, CLAWS, TOE- WALK- 

 ING 



The Keptiles are known from Amphibians, as we 

 have seen, by their scaly bodies, and by having no 

 gills at any time, and also by having the head joined 

 to the neck by only one ball-and-socket joint instead 

 of by two. The tongaes also of the two classes differ. 

 Nearly all reptiles and some fishes are scaly, bnt the 

 scales of the two classes are usually very different. 

 Those of most fishes, when present, can be scraped off, 

 or are loose and outside of the skin , while those of 

 the reptiles are mere homy folds of the skin itself and 

 do not come away. A few reptiles and many fishes 

 are scaleless, however, bnt no reptile has gUIs or gill- 

 openings, while no fish is without both of these ; they 

 are thus distinguished the one from the other. 



As we go upward, the rule is, scales for reptiles, 

 feathers for birds, and hair for mammals. If we had 

 lived in one of the long-ago geological periods (Jurassic 

 or lower), we should doubtless have seen creatures half- 

 bird half -reptile ; and feathers and scales would have 



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