Natural history of Trinidad and Tobago giant leatherback sea turtle ("Dermochelys coriacea"), the hawksbill turtle ("Eretmochelys imbricata"), the loggerhead turtle ("Caretta caretta"), the olive ridley turtle ("Lepidochelys olivacea") and the green sea turtle ("Chelonia mydas") are marine species that either nest on the islands' beaches or frequent their coastal waters. The land dwelling yellow-footed tortoise ("Geochelone denticulata") or Morrocoy as it is locally known is threatened by high levels of poaching in Trinidad. The odd mata-mata turtle ("Chelus fimbriata") is known as a waif (and is possibly a rare inhabitant) of the Nariva Swamp and other southern and eastern coastal river systems in Trinidad. The wood-turtle
History of manifolds and varieties History of manifolds and varieties The study of manifolds combines many important areas of mathematics: it generalizes concepts such as curves and surfaces as well as ideas from linear algebra and topology. Certain special classes of manifolds also have additional algebraic structure; they may behave like groups, for instance. In that case, they are called Lie Groups. Alternatively, they may be described by polynomial equations, in which case they are called algebraic varieties, and if they additionally carry a group structure, they are called algebraic groups. The term "manifold" comes from German "Mannigfaltigkeit," by Riemann. In English, "manifold" refers to