66 THE AMERICAN MUSEUM JOURNAL 
other reptiles, and the position, 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 
fie? 
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 by a moderate estimate of 
geological time. These Amphibious Dinosaurs are more ancient ~ 
than any of the extinct mammals in the adjoining hall (No. 406), 
except for a few tiny jaws in the Small Mammal Alcove. They 
were the largest animals that ever lived, excepting some of the 
whales, and certainly were the largest animals that ever walked 
on four legs. 
In proportions and appearance the Brontosaurus 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 elephant, and a remarkably small head for the size of the 
beast. The ribs, limb-bones and tail-bones are exceptionally 
solid and heavy; the vertebrz 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 purpose they are constructed with an elaborate system of 
