pian region, and westwards had open communication with the
great ocean, as indeed the ancient geographers Eratosthenes, Strabo and
Pliny believed it still had in their day. This communication began to
fail, or close up presumably in the Miocene period; and before the dawn
of Pliocene times the Sarmatian Ocean was broken up or divided into
sections, one of which was the Aralo-Caspian sea already discussed.
During the subsequent Ice Age the Caspian flowed over the steppes that
stretch away to the north, and was probably still connected with the
Black Sea (itself as yet unconnected with the Mediterranean), while
northwards it sent a narrow gulf or inlet far up the Volga valley, for
Aralo-Caspian deposits have been observed along the lower Kama in 56
deg. N. lat. Eastwards it penetrated up the Uzboi depression between the
Great and Little Balkhan ranges, so that that depression, which is
strewn (as mentioned above) with Post-Tertiary marine deposits, was not
(as is sometimes supposed) an old bed of the Oxus, but a gulf of the
Caspian. After the great ice cap had thawed and a period of general
desiccation set in, the Caspian began to shrink in area, and
simultaneously its connexions with the Black Sea and the Sea of Aral
were severed.

_Fauna_.--The fauna of this sea has been studied by Eichwald,
Kowalevsky, Grimm, Dybowski, Kessler and Sars. At the present time it
represents an intermingling of marine and fresh-water forms. To the
former belongs the herring (_Clupea_), and to the latter, species of
_Cyprinus, Perca_ and _Silurus_, also a lobster. Other marine forms are
Rhizopoda (_Rotalia_ and _Textillaria_), the sponge _Amorphina_, the
_Amphicteis_ worm, the molluscs _Cardium edule_ and other _Cardidae_,
and some Amphipods (_Cumacea_ and _Mysidae_,), but they are forms which
either tolerate variations in salinity or are especially characteristic
of brackish waters. But there are many species inhabiting the waters of
the Caspian which are not found elsewhere. These include Protozoa, three
sponges, Vermes, twenty-five Molluscs, numerous Amphipods, fishes of the
genera _Gobias, Benthophilus_ and _Cobitis_, and one mammal (_Phoca
caspia_). This last, together with some of the _Mysidae_ and the species
_Glyptonotus entomon_, exhibits Arctic characteristics, which has
suggested the idea of a geologically recent connexion between the
Caspian and the Arctic, an idea of which no real proofs have been as yet
discovered. The Knipovic