Answer:
Only two backbones and thousands of ribs.
I'm white, I'm round, but not always around. Sometimes you see me, sometimes you don't.
Until I am measured I am not known, Yet how you miss me when I have flown.
I have an eye but cannot see, You'll head inside when you see me.
There is a creature of God whose body is hardΝΎ it does not wish to eat unless you strike its head.
I met a man on the London bridge, he tipped his hat and drew his name, in this riddle I told you his name. What is it?