40. During the earthquakes which took place at the commencement of this period, one finds that organic life has been arrested, which is proved by the absence of fossils in these rocks. But, as soon as a calmer state was restored, vegetables and animal re-appeared. The conditions of vitality being changed, the atmosphere becoming purer, new species, with more perfect organization, were formed. As regards structure, the plants differed very little from those of our time.