alcyonium. 95 



Alcyonium digitatum. 



This species lias a very wide distribution in the British 

 area, and may be regarded as one of the most abundant 

 of British marine animals, as it appears to be capable of 

 adapting itself to a very great range of natural condi- 

 tions ; but although so common, it is not found in many 

 places at low tides. It is found in great numbers growing 

 on the shells of Pectens, Cardiums, and other Mollusca 

 on sandy, gravelly or shelly trawling grounds. It occurs 

 attached to rocks which are exposed at low tides, and even 

 on iron pillars of piers just below low-water mark, and 

 encrusting worm tubes on muddy bottoms. Its vertical 

 range extends from shallow water to a denth of 383 

 fathoms ("Caudan"), but probably depths of 35-40 fathoms, 

 i.e., the usual limit of wave action (as Allen has pointed 

 out) are most suitable for its maximum growth and 

 development. Geographically it extends from the coast 

 of Norway (Hardanger fjord) to the Bay of Biscay, and 

 it seems probable that there is no considerable extent of 

 the British area which is free from it. I am indebted to 

 Mr. Chadwick for the following notes as to the distribution 

 of Alcyonium digitatum in the L.M.B.C. district. " Very 

 small colonies are sometimes found at extreme low-water 

 mark in Port Erin Bay, and large ones, of both colour 

 varieties, occur in large numbers on the blocks of con- 

 crete forming the now ruined breakwater. We occa- 

 sionally dredge colonies from depths of 12 to 15 fathoms 

 in this neighbourhood. I have seen several very fine ones 

 brought up on the long lines used by our fishermen. The 

 greatest depth of which we have a record is 21 fathoms, on 

 North Bank, 7 miles W. of Peel. It is pretty generally 

 distributed all round the Manx coast. Alcyonium used to 

 be abundant and the colonies of large size on some reefs 



