33 .-- Skull of Gila Monster (_Heloderma_), for comparison of surface with skin impressions of _Trachodon_.
Enlarged to 4/3.] "The thin character of the epidermis as revealed by this specimen favors also the theory that these animals spent a large part of their time in the water, which theory is strengthened by the fact that the diminutive fore limb terminates not in claws or hoofs, but in a broad extension of the skin, reaching beyond the fingers and forming a kind of paddle.[18] The marginal web which connects all the fingers with each other, together with the fact that the lower side of the fore limb is as delicate in its epidermal structure as the upper, certainly tends to support the theory of the swimming rather than the walking or terrestrial function of this fore paddle as indicated in the accompanying preliminary restoration that was made by Charles R.
Knight working under the writer's direction.

One is drawn in the conventional bipedal or standing posture while the other is in a quadrupedal pose or walking position, sustaining or balancing the fore part of the body on a muddy surface with its fore feet.

In the distant water a large number of animals are disporting themselves.
"The designation of these animals as the 'duck-billed' dinosaurs in reference to the broadening of the beak, has long been considered in connection with the theory of aquatic habitat.

The conversion of the fore limb into a sort of paddle, as evidenced by the Sternberg specimen, strengthens this theory.
"This truly wonderful specimen, therefore, nearly doubles our previous insight into the habits and life of a very remarkable group of reptiles." _Saurolophus, Corythosaurus._ In the latest Cretaceous formation, the Lance or Triceratops beds, all the duck-billed dinosaurs are much alike, and are referred to the single genus _Trachodon_.

In somewhat older formations of the Cretacic period there were several different kinds.