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THE POPULAR SCIENCE MONTHLY, 



however, is not so great, and then let us transfer this into the 

 reptilian system. For, while a kangaroo is a warm-blooded mam- 

 mal, covered with hair, the dinosaurs were cold-blooded, scaly 

 reptiles. The anatomy of the dinosaurs resembles that of the 

 lizards and crocodiles, but in many respects it reminds us of the 

 skeleton of birds. These bird-like features appear especially in 

 the pelvis and the posterior legs, and are so striking that some 

 scientists believe that birds are the descendants of dinosaurs ; 

 others think that birds and dinosaurs originated from a common 

 ancestor. The close relationship of these two classes of animals 

 will appear to us more plausible if we remember the fact that the 

 birds of the Jurassic and Cretaceous periods resembled reptiles 

 much more than they do now — for instance, in their possession of 

 teeth. This may be said of dinosaurs in general, and we may now 

 contemplate some of their known representatives. 



If we enter the Museum of the Academy of Natural Sciences 

 in Philadelphia, the first thing that attracts our eye is an enor- 

 mous skeleton found at the left side of the entrance. It 

 represents an animal seventeen feet high, and measuring 

 from head to tail twenty-four feet. It is mounted 

 so that it stands on its hind-legs and is 

 supported by its strong and long tail, 

 while the short anterior limbs rest upon 

 a structure purporting to be a reproduc- 

 tion of a tree of past periods. If we ex- 

 amine the skeleton more closely, we 

 find that only a few bones of the 

 hind-legs and the tail are naturally 

 found fossils, while all the other 

 bones are artificial casts. But most 

 of them are exact representations of 

 the original fossil bones, which 

 are kept under glass for the 

 sake of better preservation. 

 They were found in 1858 in 



Fig 2.-HADR0SAURUB (restoration by Hawkins). the CretaCCOUS formation of 



New Jersey, and the animal 

 has been described under the name of hadrosaurus. An exact 

 imitation of this skeleton exists also in the National Museum at 

 Washington. 



The hadrosaurus is as yet the only complete mounted dinosaur 

 in America, and it must not be forgotten that some parts of this 

 skeleton were not found, but for the sake of completeness were 

 formed in analogy to the others. In Europe they have been more 

 fortunate in this respect. In the Royal Museum, at Brussels, in 

 Belgium, there is the mounted skeleton of a similar dinosaur, the 



