The pic you posted looks like a Banded Serpent star. When you say "furrier" legs, it's probably what we refer to as a Brittle star - the legs are "spiky". We have a Black Brittle star, and also what is referred to as a "Tiger" brittle - it's very dark (brown-black), but you can see faint cream-colored stripes on the legs.
As far as size, ours have been very large (16" from tip to tip) for quite a while (years), so I can't remember how quickly they grew. I love my 'Sea Monsters'!