Lichen on Lime Tree

Lichen on Lime Tree

Observation - Lichen on Lime Tree. Description: Thallus a very pale turquoise near perimeter; the central area slightly yellowish pale grey-green. Lobes have ripples rather like water surface blown by the wind.One of this large genus! But which one?

Thallus a very pale turquoise near perimeter; the central area slightly yellowish pale grey-green. Lobes have ripples rather like water surface blown by the wind.One of this large genus! But which one?