THE DEEP-SEA FAUNA. 169 
corals, solitary forms usually, are often dredged in great num- 
bers, and are in striking contrast to the extensive coral reefs of 
former geological periods, which resemble those of recent times, 
and must have flourished in shallow water under conditions of 
temperature analogous to those of the districts in which coral 
reefs are found to-day. 
The Echini characteristic of the shallower littoral districts 
were formerly, as now, mainly Clypeastride, while the Echinide, 
Cidaridx, Diadematidze, and Coelopleuride characterized the con- 
tinental areas, and the Ananchytide, Pourtalesize, Phormosom:e, 
and Galeritide probably flourished best in deep water. 
Lingula may have been from the earliest times a littoral 
species, while Terebratula and other brachiopods belonged to 
the continental, and abyssal regions. Gasteropods are found in 
deep water, but are usually of small size. The larger species 
seem to have lived, as to-day, in comparatively shallow areas, 
though a few, such as Voluta, Dentalium, and Pleurotomaria, 
lived in deep water. Of the cephalopods many are pelagic, 
others littoral, while Nautilus and Spirula are deep-sea types, 
though Verrill has dredged shells of the pelagic argonaut in 
deep water. In the older formations the huge cephalopods of 
these times were abundant in the littoral regions. | 
Among the crustacea Eryon-like forms predominate in deep 
waters, and gigantic isopods and Pygnogonide are also found af 
great depths. Accumulations of terrestrial animals and plants 
driven out to sea by the winds and currents may likewise find 
their way to deep-sea deposits. 
The remains of pelagic animals, often occurring in great 
numbers, do not always indicate an oceanic deposit, as they may 
after their death be taken by the winds and currents far from 
their habitat, and be carried considerable distances by fishes. 
The shell of Spirula is found on all tropical beaches. We find 
immense accumulations of pelagic animals, as well as of the 
dead carcasses of squids, driven ashore in quantities by storms 
or caught by the tides. The mortality among fishes is often 
very great; large shoals are hunted to the shore by predatory 
species and sharks, and our beaches are not unfrequently lined 
for long distances with fishes which have perished from sudden 
unknown causes. 
