Handbook of Paleontology 179 



the deeper waters off the more southern shores of the 

 United States. In general the arctic seas have their own 

 characteristic fauna; and so also are there genera and 

 species peculiar to the more temperate waters of Europe 

 and America and to the warm waters of the tropical seas. 

 Along the Atlantic Coast of North America four prov- 

 inces are recognized for the littoral and shallow-water 

 species of mollusks — the Arctic, the Boreal, the Trans- 

 atlantic and the Caribbean Provinces. Very cold-water 

 forms of the circumpolar region, the Arctic Province, 

 are found as far south as Newfoundland. Some of the 

 characteristic genera of the arctic fauna are found along 

 the coast of Maine and Massachusetts, as far south as 

 Cape Cod, urged southward under the influence of the 

 cold Labrador current. Among these genera are the 

 bivalves Mya, Leda, Yoldia, Astarte and the snails Buc- 

 cinum, Chrysodomus, Sipho, Trophon, Bela, Velutina, 

 Lacuna and Margarita etc. The Boreal Provinces of 

 Europe and North America correspond and as we have 

 seen in our previous discussions they possess many forms 

 in common. This province along American shores ex- 

 tends from the Gulf of St Lawrence along the New 

 England coast to Cape Cod and is characterized by such 

 bivalve genera as Mytilus, Modiola, Nucula; such genera 

 of snails as Purpura, Littorina, Lunatia, Neverita, Ac- 

 maea, and Margarita; the Chiton, and the nudibranchs 

 Eolis and Doris. The Transatlantic Province extends 

 from Cape Cod to Florida. Some forms of the boreal 

 province pass Cape Cod and live as far south as Long 

 Island sound and certain genera of the transatlantic prov- 

 ince live north of Cape Cod in Massachusetts bay though 

 they do not thrive so well in the colder waters there. 

 Cape Hatteras acts as a barrier forming a subdivision in 



