Calcareous screes of the Paris basin and its periphery, with Leontodon hyoseroides, Sisymbrium supinum, Linaria supina, Galeopsis angustifolia and many rare or endemic plants, including Viola hispida (endangered endemic), Galium timeroyi ssp. fleurotii, Iberis violetii, Iberis durandii, Biscutella neustriaca.