Turtle vs. Tortoise: http://wiki.answers.com/Q/What%27s_the_difference_between_a_turtle_and_tortoise As a non-native speaker of English I found this very interesting. As far as I can tell it's the same as Landschildkröten and Meeresschildkröten in German.
It's actually a bit more complicated than that. The usage of "tortoise" and "turtle" depends on the dialect of English being spoken. See the wikipedia entry here: http://en.wikipedia.org/wiki/Turtle#Turtle.2C_tortoise.2C_or_terrapin and these Oxford English Dictionary definition: http://oxforddictionaries.com/definition/english/tortoise?q=tortoise and http://oxforddictionaries.com/definition/english/turtle?q=turtle for more on the controversy.