364 AN INTRODUCTION TO THE STUDY OF FOSSILS 



horn upon its nose and a very large pair of horns on the top of 

 its head, while the posterior part of the skull developed into a 



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Fig. 157. — A restoration of the three-horned, neck-frilled dinosaur, Triceratops 

 prorsus, living during the uppermost Cretaceous in the lowlands of what at present 

 forms the Rocky Mountain area of North America. This reptile was twenty-five 

 feet long. Restoration by Charles R. Knight. (From Lucas, through the courtesy 

 of McCIure, Phillips & Co.) 



huge horn-covered frill margined with spines. This frill pro- 

 tected the top of the neck and gave to the skull its wedge-shaped 

 appearance, the beak being pointed, bird-like. 



Order 6, Pterosauria {Flying reptiles) 



Extinct flying reptiles with a long neck and a general bird- 

 like build. The anterior of the two pairs of limbs are large, 

 bat-like, leathery wings, the smooth membrane of which was 

 supported between the greatly elongated little finger and the 

 sides of the body (whence the name from Greek pteron, sl 

 wing, -h sauros, sl lizard). The thumb is lacking; the other 

 three fingers bear claws. Bones hollow and light. Breast- 



