458 ON THE FAUNA AND BOTTOM-DEPOSITS NEAR THE 30-FM. LINE 



practical importance. A large colony of Alcyonmm when fully ex- 

 panded offers a very considerable surface to any movement of the 

 water, and when such a colony is attached to a shell of the size of 

 Pectcn opercularis or Cardimn echinatum (which are the shells to which 

 the small colonies are generally attached on the grounds under investi- 

 gation) a very slight movement will be sufficient to overturn it. At a 

 depth of 30 to 35 fms. we are probably approaching the limit at which 

 wave action is seriously felt on the sea-bottom in this portion of the 

 Channel.* This diminution of wave action certainly seems a reasonable 

 explanation of the facts observed in the distribution of Alcyonium, 

 namely, that at depths less than 34 or 35 fms., although small colonies 

 growing on shells are common, large colonies are seldom found attached 

 to such objects, but large colonies do exist, at any rate in sheltered 

 situations, fixed to rocks or solid structures : at depths greater than 34 

 or 35 fms., on the other hand, large colonies are plentiful attached 



to shells. 



Distribution. Geographical. Bergen and Hardanger Fjords (Normau fide Hickson, 

 No. 45, p. 352) ; Kattegat (Leviusen, No. 66) ; North Sea (Schiilze, No. 105 ; Hartlaub, 

 No. 38). British Coasts ; Brittany (Pruvot, No. 98) ; Bay of Biscay {Caudan, No. 61). 



Depth. Low-water to 312-383 fathoms (Caudan). 



Sarcodictyon catenata (Chart I.). The red variety is found growing, 

 sometimes in considerable quantity, on old shells (chiefly old and worn 

 shells of Lutraria elliptica and Pecten opercularis), and is generally 

 most numerous on clean shell gravel, though by no means confined to 

 such ground. It was most regularly taken on the shell gravel west 

 of the Eddystone (Ground XVI. and some hauls of XIV.). On 

 Ground VII., south of the Eddystone, it was present in one haul only 

 (haul 100), where it was very abundant, growing on a flat piece of red 

 Trias stone. It was occasionally taken on Grounds X., XIII., XV., and 

 IV. (haul 39 only), in the neighbourhood of the Eddystone, and was 

 not unfrequent on the Bolt Head Shell Gravel and on the Prawle 

 Stony Ground. 



The species was not taken on the fine sand grounds, I., II., III., V., 



VI., and VIII. 



Distribution. Shetland (Norman, No. 90) ; west coast of Scotland and Lish Sea 

 (Herdman,No. 40, p. 319, and No. 41, VoL IX.); Brittany and Mediterranean (Pruvot, 

 No. 98). 



On nuUipore ground, on sand and shell, on shell sand and small gravel, on shells, 

 stones, and echinoderm spines, and on stones and mud. 10-40 fathoms (Herdman, No. 

 41). 



Gorrjonia verrucosa (red variety, G. Cavoliiii, v. Koch) was taken only 

 in haul 3, on the Prawle Stony Ground (XVIII.). The trawl had here 

 been over a patch of rocky ground, and came up very much torn. The 

 species is always obtained on tocky ground in this neighbourhood. 



* See page 375, ante. 



