Natural History of the Ihitish Seas. 337 



belong to this region, to which, on account of the plant-like 

 zoophytes abounding in it, the name of Coralline Zone has 

 been applied. The majority of the rarer shell-fish of our seas 

 have been procured from this region. 



Below 50 fathoms i^ the Region of Deep-sea Corals, 

 so styled because hard and strong true corals of considerable 

 dimensions are found in its depths. In the British seas it is 

 to be looked for around the Zetlands and Hebrides, where 

 many of our most curious animals, forms of zoophytes and 

 Echinoderms, have been drawn up from the abyss of the 

 ocean. Its deepest recesses have not as yet been examined. 

 Into this region we find that not a few species extend their 

 range from the higher zones. When they do so they often 

 change their aspect, especially so far as colour is concerned, 

 losing brightness of hue and becoming dull-coloured or even 

 colourless. In the lower zones it is the association of species 

 rather than the presence of peculiar forms which gives them 

 a distinctive character. All recent researches, when scien- 

 tifically conducted, have confirmed this classification of pro- 

 vinces of depth. When we have an apparent exception, as 

 in the case of the submarine ravine off the Mull of Galloway, 

 dredged by Captain Beech ey and recorded by Mr Thompson, 

 in which though it is 150 fathoms deep, the fauna is that 

 of the coralline zone, we must seek for an explanation of the 

 anomaly by enquiring into the geological history of the area 

 in question. In this particular instance there is every reason 

 to believe that the ravine mentioned is of a very late date 

 compared with the epoch of diffusion of the British Fauna. 



When we trace the horizontal distribution of creatures in 

 the British seas, we find that though our area must be mainly 

 or almost entirely referred to one of the great European 

 marine provinces, that to which the Lecturer has given the 

 name of Celtic, yet there are subdivisions within itself 

 marked out by the presence or absence of peculiar species. 

 The marine fauna and flora of the Channel Isles present cer- 

 tain differences, not numerous but not the less important, 

 from that of the south-western shores of England, which in 

 its turn differs from that of the Irish sea, and it again from 

 that of the Hebrides. The Cornish and Devon sea fauna and 

 " VOL. L. NO. C. — APRIL 1851. Y 



