Of the three Guyanas on the north coast of South America, Suriname is the middle one, lying between French Guyana to the east and British Guyana to the west. The frontiers between these three countries are formed by the Marowijne River (Suriname — French Guyana) and the Courantyne River (Suriname — British Guyana). In general the Guyanas are much alike in geographical features — covered with tropical rain forest for the most part and with savannas and swamps for the rest. The freshwater molluscs live in the large rivers and the bush creeks in the hinterland, and in the swamps, canals and trenches in the more or less cultivated coastal plain.