37 .-- Skulls of Horned Dinosaurs.

The lower row, _Ceratops_, _Styracosaurus_, _Monoclonius_, are from the Middle Cretacic (Belly River formation) of Alberta; _Anchiceratops_ is from the Upper Cretacic (Edmonton formation) of Alberta; _Triceratops_ and _Torosaurus_ from the uppermost Cretacic (Lance formation) of Wyoming.] These were the first of a long series of discoveries which through scientific and popular descriptions have made the Horned Dinosaurs familiar to the world.

Most of them are still very imperfectly known, and of their evolution and earlier history we know very little as yet.
But we can form a fairly correct idea of their general appearance and habits and of the part they played in the world of the late Cretacic.
So far as known they were limited to North America.

The most striking feature of the Horned Dinosaurs is the gigantic skull, armed with a pair of horns over the orbits and a median horn on the nasal bones in front, and with a great bony crest projecting at the back and sides.
In some species the skull with its bony frill attains a length of seven or even eight feet and about three feet width; the usual length is five or six feet and the width about three.

In the best known genus, _Triceratops_, the paired horns are long and stout and the front horn quite short or almost absent, while in _Monoclonius_ these proportions are reversed, the front horn being long while the paired horns are rudimentary.
The teeth are in a single row but are broadened out into a wide grinding surface.