ave existed, and Monocotyledonous plants or
Endogens are very poorly represented. With the Upper Cretaceous,
however, a new era of plant-life, of which our present is but
the culmination, commenced, with a great and apparently sudden
development of new forms. In place of the Ferns, Cycads, and
Conifers of the earlier Mesozoic deposits, we have now an
astonishingly large number of true Angiospermous Exogens, many
of them belonging to existing types; and along with these are
various Monocotyledonous plants, including the first examples of
the great and important group of the Palms. It is thus a matter
of interest to reflect that plants closely related to those now
inhabiting the earth, were in existence at a time when the ocean
was tenanted by Ammonites and Belemnites, and when land and sea
and air were peopled by the extraordinary extinct Reptiles of
the Mesozoic period.

[Illustration: Fig. 186.--Cretaceous Angiosperms. a. _Sassafras
Cretaceum; b, Liriodendron Meekii; c, Leguminosites Marcouanus;
d, Salix Meekii_. (After Dana.)]

As regards animal life, the _Protozoans_ of the Cretaceous period
are exceedingly numerous, and are represented by _Foraminifera_
and _Sponges_. As we have already seen, the White Chalk itself is
a deep-sea deposit, almost entirely composed of the microscopic
shells of _Foraminifers_, along with Sponge-spicules, and organic
_debris_ of different kinds (see fig. 7). The green grains which
are so abundant in several minor subdivisions of the Cretaceous,
are also in many instances really casts in glauconite of the
chambered shells of these minute organisms. A great many species
of _Foraminifera_ have been recognised in the Chalk; but the
three principal genera are _Globigerina, Rotalia_ (fig. 187),
and _Textularia_--groups which are likewise characteristic of
the "ooze" of the Atlantic and Pacific Oceans at great depths.
The flints of the Chalk also commonly contain the shells of
_Foraminifera_. The Upper Greensand has yielded in considerable
numbers the huge _Foraminifera_ described by Dr Carpenter under
the name of _Parkeria_, the spherical shells of which are composed
of sand-grains agglutinated together, and sometimes attain a
diameter of two and a quarter inches. The Cretaceous Sponges are
extremely numerous, and occur under a great number of varieties
of shape and structure; but the two most characteristic genera
are _Siphonia_ and _Ventriculites_, both of which are exclusively
confined