pipe fishes, and blennies: the _seaweed region_, extending from low-
water-mark to a depth of 450 feet, with its wrasses, rays, and flat fish;
and the _deep-sea region_, from 450 feet to 1500 feet or more, with
its file-fish, sharks, gurnards, cod, and sword-fish.

More than twenty years later, M.M. Audouin and Milne Edwards carried out
the principle of distinguishing the Faunae of different zones of depth
much more minutely, in their "Recherches pour servir à l'Histoire
Naturelle du Littoral de la France," published in 1832.

They divide the area included between highwater-mark and lowwater-mark of
spring tides (which is very extensive, on account of the great rise and
fall of the tide on the Normandy coast about St. Malo, where their
observations were made) into four zones, each characterized by its
peculiar invertebrate inhabitants. Beyond the fourth region they
distinguish a fifth, which is never uncovered, and is inhabited by
oysters, scallops, and large starfishes and other animals. Beyond this
they seem to think that animal life is absent.[3]

[Footnote 3: "Enfin plus has encore, c'est-à-dire alors loin des côtes,
le fond des eaux ne paraît plus être habité, du moms dans nos mers, par
aucun de ces animaux" (1. c. tom. i. p. 237). The "ces animaux" leaves
the meaning of the authors doubtful.]

Audouin and Milne Edwards were the first to see the importance of the
bearing of a knowledge of the manner in which marine animals are
distributed in depth, on geology. They suggest that, by this means, it
will be possible to judge whether a fossiliferous stratum was formed upon
the shore of an ancient sea, and even to determine whether it was
deposited in shallower or deeper water on that shore; the association of