What's the name of this flower with serrated petals? I tried looking it up in a encyclopedia, but I couldn't get anything.

I had to get a tetanus shot after slicing my little finger with the serrated edge of a butter knife.

Before us lay the dark bulk of the house, its serrated roof and bristling chimneys hard outlined against the silver-spangled sky.

The knife's serrated edge makes it perfect for cutting such things as bread.