The sub-Crag detritus-bed, sometimes called the nodule bed, or the Suffolk bone bed, was first brought to the notice of geologists by the late Prof. Henslow, who, in 1843, discovered that the Crag contained many nodules rich in lime phosphates, of great agricultural and commercial value—mostly known as “Coprolites,” though not of coprolitic origin, unless the spirally-formed bodies are the coprolitic rejectamenta of sharks or other animals having a spiral intestine.

The detrital bed is principally made up of the following constituents:—(1) Phosphatic nodules (the so-called Coprolites). (2) Sandstone nodules or box-stones. (3) Rocks of various ages earlier than the Crag. (4) Large chalk flints, many unrolled. (5) Rolled and waterworn bones, usually much mineralised. (6) Cetacean beaks, and other bones. (7) Bones and teeth of land mammalia. (8) Wood and other items, chiefly of uncertain age.

The above groups are of very different periods, and I propose treating each one separately, their origin and mode of occurrence as far as is known, or suggested.