320 Professor Edward Forbes on the Light thrown on 



in the British seas,* and more lately in the ^gean, has been 

 to define a series of zones or regions in depth, and to ascer- 

 tain specifically the animal and vegetable inhabitants of each. 

 Regarding the tract between tide-marks as one region, which 

 I have termed the Littoral Zone, we find a series of equiva- 

 lent regions, succeeding it in depth. In the British seas, the 

 littoral zone is succeeded by the region of Laminariae, tilled 

 by forests of broad-leaved Fuci, among which live some of the 

 most brilliantly coloured and elegant inhabitants of the ocean. 

 This is the chosen habitat of Lacimce, of Rissooe, and of Nu- 

 dibranchous mollusca. A belt generally of mud or gravel, in 

 which numerous bivalve mollusca live, intervenes between the 

 laminarian zone (in which the Flora of the sea appears to 

 have its maximum), and the region of Corallines, which, 

 ranging from a depth of from 20 to 40 fathoms, abounds 

 in beautiful flexible zoophytes and in numerous species of 

 Mollusca and Crustacea, to be procured only by means of 

 the dredge. The great banks of Monomyarious Mollusca, 

 which occur in many districts of the Northern Seas, are for the 

 most part included in this region, and affbrd the zoologist his 

 richest treasures. Deeper still is a region as yet but little 

 explored, from which we draw up the more massy corals 

 found on our shores, accompanied by shellfish of the class 

 Brachiopoda. In the Eastern Mediterranean (where, through 

 the invaluable assistance afforded by Captain Graves, and the 

 Mediterranean Survey, I have been enabled to define the re- 

 gions in depth, to an extent, and with a precision which, 

 without similar aid, cannot be hoped for in the British seas), 

 between the surface and the depth of 230 fathoms, the lowest 

 point I had an opportunity of examining, there are eight welU 

 defined zones, corresponding in part, and presenting similar 

 characters with those which I have enumerated as presented 

 by the sea-bed in the North. The details of these will be 

 given in the forthcoming volume of the Transactions of the 



* The first notice of these was published in th^ Edinburgh Academic 

 Annual for 1840. 



