“The Silurian Period-the grandest of all the Periods,-and, as yet, apparently the seed-time of all succeeding life.” LifeScienceEvolutionPeriodsSucceedSeeds Book:Thesauricus Siluricus: The flora and fauna of the Silurian period. With addenda (from recent acquisitions). Source: Thesauricus Siluricus: The flora and fauna of the Silurian period. With addenda (from recent acquisitions).