54 
Belemnoziphius, teeth of Sharks and Crustacea, derived from 
the London Clay as in the Red Crag. At one spot in the 
Red Clay, 10 feet thick, the phosphate nodules are inter- 
mingled with a few shells, and under this is a seam of these 
concretions, with shelly Red Crag below, Mr. Prestwich con- 
siders all these so-called Coprolites to have been originally 
derived from the Coralline Crag. Numerous remains of Mam- 
malia and Cetacea, more or less mineralized and worn, and 
most of which are probably extraneous, are associated with 
these nodules. 
Passing downwards in the order of Geological succession, 
and at a still later period of working, certain brown and 
black nodules of irregular shape and various sizes, which had 
long been known to occur in the upper Green Sand, at Cam- 
bridge, but had not formerly been supposed to be either so 
extensive or valuable for economical purposes, have been 
largely worked and extensively applied to these uses, and a 
very large quantity have been made into a valuable bone 
manure. The pits round Cambridge have now been dug for 
many years, and many of them are entirely worked out and 
new ones are opened there, elsewhere, and in Bedfordshire, 
though of older geological date. In the former county the bed is 
comparatively thin, but abounds in these phosphatic concre- 
tions, it has, however, a tolerably wide range, but being 
nowhere very thick, it.will not be very long before it is entirely 
exhausted. Thin as the stratum is, however, at Cambridge 
it abounds in fossils of the Cretaceous period, and the diggings 
have led to the discovery of many rare and important forms of 
life, especially Pterodactyles, Saurians, Amphibia, of which a 
fine collection may be seen in the Woodwardian Museum, in 
that University. For most of the earlier and more recent 
acquisitions it is mainly indebted to my valued old friend and 
former Geological tutor, the venerable Professor Sedgwick. 
