ITS EXTENT AND ITS MARINE FAUNA. 31 



to the south some of them are dredged off the west coast of Ireland 

 and even off the coast of Brittany, but it is only in the North 

 Sea that they occur in such shallow water as 50 to 60 fathoms. 

 It is from this so-called " Dogger-Bank " source that conchologists 

 still for the most part obtain their specimens of these Mollusca. 

 The species are Modiolaria nigra. Gray, Pmiopea norvegica, 

 Spengler, Calliostoma occidentale, Mighels, Liomesus Dalei, 

 J. Sowerby, Volutopsis norvegiciis, Chemnitz, Beringius Turtoni, 

 Bean, Buccinofusus herniciensis, King, Lunatia pallida, Brod. 

 and Sow., and Amauropsis islandicus, Gmeliu. Other shells 

 of considerable interest which accompany these are Scalaria 

 Trevelyana, Leach, a large form of Tritonofusus gracilis, Costa, 

 named by Jordan var. Belliana, and a giant form of Modiola 

 modiolus, Linn., reaching 7 inches in greatest diameter. 



There is an interesting case of one species of the Polyzoa which 

 appears to have migrated in a particular form from the southern 

 coasts of France to the coast of Norway, but is unknown in the 

 British Islands. The species is Electra pilosa, Linn., which is 

 found on every part of the British coast, but always in an 

 incrusting form, and no single example has ever been met with 

 assuming a state independent of the seaweed, shell, or stone to 

 which it adheres. In the extreme south of France, however, for 

 example at Biarritz, a very beautiful form, Electra verticellata, 

 Lamouroux, is found, which may or may not be a very extreme 

 variation of E. pilosa, but, at any rate, in the Bay of Biscay the 

 true E. p)ilosa occurs, growing erect as a little shrub. I have 

 specimens, again, of this erect form from the Belgian coast, where 

 it is extraordinarily abundant, and Pallas, writing one hundred 

 and twenty -seven years ago, stated that it was thrown up there 

 on the shore in cart-loads. Northwards I have dredged this free 

 form on the Norwegian coast, in the Bergen Fiord, and even 

 so far north as Flor'6. In this latter locality it takes upon itself 

 a marvellous variety in cell-building, and assumes very varied 

 forms of free growth.* The absence of the free-living forms 

 on the British coast is very remarkable, and it would appear 

 as though the larval state of this variety had never lieen able 

 to migrate across the Channel. There are other species on 

 the Belgian coast which are unknown in our seas. 



Much interest attaches to the investigation of the fauna of 

 the Continental Shelf of the west of Ireland, now being carried 

 out by the Commission of the Sea and Inland Fisheries of 



* A. M. Ndrraan, " A Month in tlie Troiullijcni Fiord," ' Aim. Mai;'. Xat. 

 Hist.,' ser. 6, vol. xiii, 1894, p. 113. ' 



