se chains now rise; for Nummulites and
their accompanying Testacea were unquestionably inhabitants of
salt water."

[Illustration: Fig. 214.--_Nummulina loevigata_. Middle Eocene.]

The _Coelenterates_ of the Eocene are represented principally
by _Corals_, mostly of types identical with or nearly allied to
those now in existence. Perhaps the most characteristic group
of these is that of the _Turbinolidoe_, comprising a number of
simple "cup-corals," which probably lived in moderately deep
water. One of the forms belonging to this family is here figured
(fig. 215). Besides true Corals, the Eocene deposits have yielded
the remains of the "Sea-pens" (_Pennatulidoe_) and the branched
skeletons of the "Sea-shrubs" (_Gorgontidoe_).

The _Echinoderms_ are represented principally by Sea-urchins, and
demand nothing more than mention. It is to be observed, however,
that the great group of the Sea-lilies (_Crinoids_) is now verging
on extinction, and is but very feebly represented.

Amongst the _Mollusca_, the _Polyzoans_ and _Brachiopods_ also
require no special mention, beyond the fact that the latter are
greatly reduced in numbers, and belong principally to the existing
genera _Terebratula_ and _Rhynchonella_. The Bivalves
(_Lamellibranchs_) and the Univalves (_Gasteropods_) are exceedingly
numerous, and almost all the principal existing genera are now
represented; though less than five percent of the Eocene _species_
are identical with those now living. It is difficult to make any
selection from the many Bivalves which are known in deposits of
this age; but species of _Cardita, Crassatella, Leda, Cyrena, Mactra,
Cardium, Psammobia_, &c., may be mentioned as very characteristic.
The _Caradita planicosta_ here figured (fig. 216) is not only very
abundant in the Middle Eocene, but is very widely distributed,
ranging from Europe to the Pacific coast of North America. The
_Univalves_ of the Eocene are extremely numerous, and generally
beautifully preserved. The majority of them belong to that great
section of the _Gasteropods_ in which the mouth of the shell
is notched or produced into a canal (when the shell is said to be
"siphonostomatous")--this section including the carnivorous and
most highly-organized groups of the class. Not only is this the
case, but a large number of the Eocene Univalves belong to types
which now attain their maximum of development in the warmer regions
of the globe. Thus we find numerous species of