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[♦ This marine fauna can be divided into groups according 

 to the status of the various species, whether these be residents, 

 migrants, irregular visitors, or accidental stragglers. The 

 first of these include most of the familiar fishes, molluscs, 

 echinoderms, worms, and sea anemones of our shores ; and 

 these animals, especially the mollusca, can be further sub- 

 divided into groups, corresponding to the geographical regions 

 to which they belong. Generally speaking the molluscan 

 fauna of Great Britain, forms part of the Celtic Province 

 of marine conchologists. This province also includes the 

 coasts of the North Sea, the Baltic, Sweden, and Denmark. 

 Local species characteristic of this geographical region are 

 Cardium edule, Mya arenaria, Mytilus edulis, Pecten maximus, 

 Ostrea edulis and numerous others. 



Intermingled with these Celtic species are others ranging 

 much further northwards, and generally typical of the Boreal 

 and Arctic Provinces. To the first of these provinces, cor- 

 responding to the west coast of Norway. Iceland, the 

 Shetland and ^Faroe Islands, raid the north coast of North 

 America, belong such local molluscs as Molis despecta 

 and Doto fragilis, two sea-slugs ; Buccinum undatum, Liitorina 

 ritdis. Lacuna divaricata, Skenia planorbis, Gibbula cineraria, 

 Modiolaria discors, and Solen ensis ; and the species which 

 range into the Arctic Province and there mix with true 

 Arctic shells, include Chrysodomus antiqua, Sipho islandicus, 

 Nassa incrassata, Acmea testudinalis, Turtonia minuta, and 

 Saxicava rugosa, 



Two species found at Redcar may be cited as examples 

 of forms, which extend southwards into the Lusitanian Pro- 

 vince ; an area embracing the Mediterranean and the coasts 

 of France and Spain. These two species are Chione gallina 

 and Tellina tenuis. 



In a similar manner the other marine organisms of our 

 coast might be classified, but it must be carefully borne in 

 mind that such divisions are not exact. Owing to the absence 

 of barriers to dispersal marine animals often have a very 

 much wider geographical distribution than land animals. 

 Hence some marine shells are genuine cosmopolitans, being 

 found in all seas. The Common Mussel (Mytilus edulis) 

 and the Boring Shell [Saxicava rugosa) are said to belong to 



