The ribs, limb-bones and tail-bones are exceptionally solid and heavy; the vertebrae 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 the attachment of the huge muscles, the largest possible articulating surfaces, and the necessary strength at all points of strain.

For this purpose they are constructed with an elaborate system of braces and buttresses of thin bony plates connecting the broad articulating surfaces and muscular attachments, all the bone between these thin plates being hollowed into a complicated system of air-cavities.

This remarkable structure can be best seen in the unmounted skeleton of _Camarasaurus_, another Amphibious Dinosaur." (The scientific name _Camarasaurus_=chambered lizard, has reference to this peculiarity of construction.) "The teeth of the Brontosaurus indicate that it was an herbivorous animal, feeding on soft vegetable food.

Three opinions as to the habitat of Amphibious Dinosaurs have been held by scientific authorities.

The first, advocated by Professor Owen, who described the first specimens found sixty years ago (1841-60) and supported especially by Professor Cope, has been most generally adopted.