CHAPTER III.
ARRANGEMENT OF FOSSILS IN STRATA--FRESHWATER AND MARINE.
Successive deposition indicated by fossils--Limestones formed of corals and shells--Proofs of gradual increase of strata derived from fossils--Serpula attached to spatangus--Wood bored by Teredina--Tripoli and semi-opal formed of infusoria--Chalk derived principally from organic bodies--Distinction of freshwater from marine formations--Genera of freshwater and land shells--Rules for recognizing marine testacea--Gyrogonite and chara--Freshwater fishes--Alternation of marine and freshwater deposits--Lym-Fiord 21