[Illustration: Fig. 213.--_Napadites ellipticus_, the fruit of
a fossil Palm. London Clay, Isle of Sheppey.]
As regards the _animals_ of the Eocene period, the _Protozoans_
are represented by numerous _Foraminifera_, which reach here their
maximum of development, both as regards the size of individuals and
the number of generic types. Many of the Eocene Foraminifers are of
small size; but even these not uncommonly form whole rock-masses.
Thus, the so-called "Miliolite Limestone" of the Paris basin, largely
used as a building-stone, is almost wholly composed of the shells
of a small species of _Miliola_. The most remarkable, however, of
the many members of this group of animals which flourished in
Eocene times, are the "Nummulites" (_Nummulina_), so called from
their resemblance in shape to coins (Lat. _nummus_, a coin). The
Nummulites are amongst the largest of all known _Foraminifera_,
sometimes attaining a size of three inches in circumference;
and their internal structure is very complex (fig. 214). Many
species are known, and they are particularly characteristic of
the Middle and Upper of these periods--their place being sometimes
taken by _Orbitoides_, a form very similar to the Nummulite in
external appearance, but differing in its internal details. In
the Middle Eocene, the remains of Nummulites are found in vast
numbers in a very widely-spread and easily-recognised formation
known as the "Nummulitic Limestone" (fig.
Pages:
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436