Sea turtle Sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder cryptodira. The seven existing species of sea turtles are: the green, loggerhead, Kemp's ridley, olive ridley, hawksbill, flatback, and leatherback. The majority of a sea turtle's body is protected by its shell. The turtle's shell is divided into two sections: the carapace (the dorsal portion) and the plastron (the ventral portion). The shell is made up of smaller plates called scutes. The leatherback is the only sea turtle that does not have a hard shell. Instead, it bears a mosaic
History of manifolds and varieties spaces with a differentiable or topological structure, while "variety" refers to spaces with an algebraic structure, as in algebraic varieties. In Romance languages, manifold is translated as "variety" – such spaces with a differentiable structure are literally translated as "analytic varieties", while spaces with an algebraic structure are called "algebraic varieties". Thus for example, the french word "" means topological manifold. In the same vein, the Japanese word "" (tayōtai) also encompasses both manifold and variety. ("" (tayō) means various.) Ancestral to the modern concept of a manifold were several important results of 18th and 19th century mathematics. The oldest