8 THE AMERICAN MUSEUM JOURNAL 



other reptiles, and the ]X)siti()n, size and action of the principal 

 muscles were carefully worked out. Then the corresponding 

 bones of the Brontosaurus were studied and the position and 

 size of the attachments of the corresponding muscles were marked 

 out, so far as they could be recognized from the scars and pro- 

 cesses preserved on the bone. The Brontosaurus limbs were 

 then provisionally articulated and posed, and the position and 

 size of each muscle were represented by a broad strip of paper 

 extending from its origin to its insertion. The action and play 

 of the muscles on the limb of the Brontosaurus could then be 

 studied, and the bones adjusted until a proper and mechanically 

 correct pose was reached. The limbs were then permanently 

 mounted in these poses, and the skeleton as it stands is believed 

 to represent, as nearly as study of the fossil enables us to know, 

 a characteristic position that the animal actually assumed during 

 life. 



The Brontosaurus was one of the largest of the Amphibious 

 Dinosaurs or Sauropoda, a race of gigantic reptiles which flour- 

 ished during the Jurassic or Middle Period of the Age of Reptiles, 

 — some eight millions of years ago bv a moderate estimate of 

 geological time. These Amphibious Dinosaurs are more ancient 

 than any of the extinct mammals in the adjoining hall (Xo. 406), 

 except for a few tiny jaws in the Small Alammal Alcove. They 

 were the largest animals that ever live;^, excepting some of the 

 whales, and certainly were the largest animals that e\'er walked 

 on four legs. 



In proporticms and appearance the Brontosauinis was quite 

 unlike any living animal. It had a long thick tail like the lizards 

 and crocodiles, a long flexible neck like an ostrich, a thick, short, 

 slab-sided body and straight, massive, post-like limbs suggesting 

 the ele]')hant, and a remarkably small head for the size of the 

 beast. The ribs, limb-bones and tail-bones are exceptionally 

 solid and heavy; the vertebne of the back and neck, and the 

 skull, on the contrary, are constructed so as to combine the 

 minimum of weight with the large surface necessary for attach- 

 ment of the huge muscles, the largest possible articulating sur- 

 faces, and the necessary strength at all points of strain. For 

 this pur])ose they are constructed with an elaborate system of 



