Aren't red belly blacks an elapid (cobra relative)?
I was always amused by folks who insisted that snakes were "venomous, not poisonous." Of course, I used to live in Oregon where we have garter snakes that retain enough newt venom in their livers to poison foxes, crows, and other small predators that eat them. As a kid we knew that rattlesnakes were bad if they bit you, and you didn't let little tiny dogs eat garter snakes near creeks. Of course, the ideal was to teach the fool dog to leave all snakes strictly alone.
In all fairness though there are only two species of snake that are actually poisonous, garter snakes and rhabdophis snakes. In most cases venomous is the correct word.