Some Observations on the Upper Greensand Formation of Cambridge

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Abstract
The so-called Upper Greensand formation around Cambridge consists of a Chalk-marl, with various inclusions disseminated throughout it. These inclusions are separated for manufacturing-purposes from the Chalk-marl by levigation, and sorted by a process of sifting into (i) larger bodies, which remain in the sieve, and (ii) smaller ones, which pass through it. The larger bodies consist almost entirely of the so-called “Coprolites;” and the smaller ones form the so-called “Greensand,” which gives its name to the formation. The Coprolites .—In all cases the coprolites are the result of the fossilization of organic matter or of the immediate products of its decomposition. The connexion between animal matter and the formation of coprolite is one of the most obvious facts of the whole subject. The bones of reptiles and fishes are incrusted with coprolite precisely on those parts where cartilage was most abundant. The palates of fish such as Pycnodus are not incrusted on their free surfaces; but their attached surfaces, once covered with cartilaginous tissue, are now quite imbedded in coprolite. In Crustacea such as Palœocorystes the under surface of the body, where animal matter could easily escape, is often one mass of coprolite; while the back of the carapace, which was not covered with animal, is generally free from incrustation. Many other examples might be cited, all pointing to the intimate connexion between the presence of animal matter and phosphatic deposition. The basis of animal matter was derived from various sources; the fossil remains of Vertebrata, Crustacea, Echinodermata, Mollusca, and so

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