fessor Marsh published a brief notice of what he supposed
to be a fossil bison horn found near Denver, Colorado. Two years later
the explorations of the lamented John B. Hatcher in Wyoming and
Montana resulted in the unexpected discovery that this horn belonged
not to a bison but to a gigantic horned reptile, and that it belonged
not in the geological yesterday as at first thought, but in the far
back Cretacic, millions of years ago. For Mr. Hatcher found complete
skulls, and later secured skeletons, clearly of the Dinosaurian group,
but representing a race of dinosaurs whose existence, or at least
their extraordinary character, had been quite unsuspected. It appeared
indeed that certain teeth and skeleton bones previously discovered by
Professor Cope were related to this new type of dinosaur, but the
fragments known to the Philadelphia professor gave him no idea of what
the animal was like, although with his usual acumen he had discerned
that they differed from any animal known to science and registered
them as new under the names of _Agathaumas_ 1873 and _Monoclonius_
1876. Professor Marsh re-named his supposed bison "_Ceratops_" (_i.e._
"horned face") and gave to the closely related skulls discovered by
Mr. Hatcher the name of _Triceratops_ (_i.e._ "three horned face"),
while to the whole group he gave the name of Ceratopsia.

[Illustration: Fig. 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