502 THE OCEAN WORLD. 
The observations of Milne-Edwards, Audouin, and Professor 
Edward Forbes, have led to the division of the sea into four zones :— 
The deep sea Coral zone, from fifty to 100 fathoms; the Coralline 
zone from fifteen to fifty fathoms; the Laminarian zone, which 
stretches from fifteen fathoms to low water; and the Littoral zone, 
between high and low water marks. 
The great stronghold of Crania, Thetis, Nezra, Voldia, Dentalium, 
and Scissurella, is in the deep sea Coral zone ; while Buccinum, Fusus, 
Pleurotoma, Natica, Aporrhais, Philine, and Velutina, which are 
among the most ravenous and predatory of molluscs, are found in 
the Coralline zone. They attack the bivalves, whose shells among 
the relics of former seas, as in those of the present, show evidence 
of assaults and murder. 
The principal genera of the Laminarian zone are the different 
genera of the Nudibranchiata, and such genera as Aplysia, Trochus, 
Navicella, Rissoa, and Lacuna, which feed so much on the seaweed 
of this region. 
The Littoral zone, which, being accessible as the tide recedes, is 
best known, affords Cardium, Mytilus, Tellina, Solen, Trochus, 
Patella, Littorina, and Purpura; or in plain English, cockles, mussels, 
razor-fish, limpets, periwinkles, and tingles—species which are the 
first to attract our attention, and which are so much used for food. 
Nothing was known at the time of the translation of this work of 
the discoveries since made by Sars, Wyville Thomson, Pourtales, 
and others, as to what may now be well called the Deep Sea fauna 
which live in depths of from 100 to 1,500 fathoms. 
