Top Shell or Trochus

I only found these darker green coloured shells empty, washed up in rock pools close to the beach. They were larger than the ones I saw clinging to the rocks. According to wikipedia "The habitat defines its color. On sheltered shores it has a lighter and uniform color (yellow, brown, orange or olive green). On exposed shores its color is darker and chequered." These ones were a good inch or a little larger in size.