And it does seem to refer to that in English. Should it, though? Turtles in the narrow sense of sea turtles (Chelonioidea) are an inner branch of the whole Testudines tree, making tortoises unnecessarily paraphyletic (incomplete). It would be more logical to make tortoises the equivalent of Testudines and turtles the equivalent of Chelonioidea. Alas, English taxonomy is not always following the evolutionary logic.