Fig. 38.—Skull of Triceratops from the Lance formation in Wyoming, one-eighteenth natural size. The length of the horns is 2 feet, 9½ inches. The rostral bone or beak, and the lower jaw, are lacking; in the illustration on the cover they have been restored in outline. This fine skull was discovered by George M. Sternberg, and purchased for the Museum by Mr. Charles Lanier in 1909.
TRICERATOPS.
This is the best known of the Horned Dinosaurs, as various skulls and partial skeletons have been found from which it has been possible to reconstruct the entire animal. There is a mounted skeleton in the National Museum, another will shortly be mounted in the American Museum, and there are skulls in several American and European museums.
Triceratops exceeded the largest rhinoceroses in bulk, equalling a fairly large elephant, but with much shorter legs. The great horns over the eyes projected forward or partly upward; in one of our skulls they are 33½ inches long. During life they were probably covered with horn increasing the length by six inches or perhaps a foot. The ball-like condyle for articulation of the neck lies far underneath, at the base of the frill, almost in the middle of the skull.
Fig. 39.—Skull of Monoclonius, a horned dinosaur from the Cretacic (Belly River formation) of Alberta. One-fifteenth natural size. The horns over the eyes are rudimentary, and the nasal horn large, reversing the proportions in Triceratops.
Monoclonius, Ceratops, etc. The Triceratops and another equally gigantic Horned Dinosaur, Torosaurus, were the last survivors of their race. In somewhat older formations of Cretacic age are found remains of smaller kinds, some of them ancestors of these latest survivors, others collaterally related. None of these have the bony frill completely roofing over the neck as it does in Triceratops. There is always a central spine projecting backwards and widening out at the top to the bony margin of the frill which sweeps around on each side to join bony plates that project from the sides of the skull top. This encloses an open space or "fenestra," so that the neck was not completely protected above. Sometimes the margin of the frill is plain, at other times it carries a number of great spikes, like a gigantic Horned Lizard (Phrynosoma).
Fig. 40.—Outline sketch restoration of Triceratops, from the mounted skeleton in the National Museum.