Chad over at Digital Dream Machine links to some great illustrations by Pixar artisan Ricky Nierva. In doing so, Chad also includes this great bit of trivia from Stop Motion Master Ray Harryhausen:
the creature in It Came From Beneath The Sea featured only 6 appendages, not only to save on production costs, but also because there would be fewer of them for Ray to keep track of when animating. The viewer makes the assumption that the other two are underwater or behind structures. A clever film trick from a true master.