PEJfR0SE -3 PHOSPHATES OF ENGLAND. 95 
cases it rests directly on the London Clay, the Coralline Crag having 
been eroded. The two divisions of the Red Crag are often very difficult 
to distinguish. The only difference is that the lower division usually 
has more shells scattered through it. According to Professor Prestwich, 
the lower division includes all the beds going under the name of red 
and Norwich Crag, while the upper division includes the Chillesford 
sands and clays. Both the Coralline and the Red Crags belong to the 
Upper Pliocene perioif and are of the same age as the Upper Antwerp 
Crag. 1 
The phosphate beds occur at the base of the Coralline and Red Crags 
and immediately over the London Clay. The bed sometimes thins out, 
and at other times it separates into two seams, divided only by a few 
feet of shelly crag. Occasionally, also, nodules, and seams of nodules, 
are found running through all parts of the Red Crag, though the bed at 
its base is generally the largest and most continuous. The phosphate 
bed consists of a mass of phosphatic nodules and shell casts, siliceous 
pebbles, teeth of cetacea and sharks, and many mammal bones, besides 
occasional fragments of Lower Greensand chert, granite, and chalk 
flints. There are numerous fossils and shells, Gardium edule, Pectim- 
culiis glycymeris, Cyprina islandica, and other forms. The bed varies 
from 2 to 18 inches in thickness. The nodules vary considerably in 
both quality and quantity. They are at times of a compact and brittle 
nature, while at others they are tough and siliceous. They average 
about 53 per cent, phosphate of lime and 13 per cent, phosphate of iron. 
The quantity of bones in the beds also varies very much. Sometimes 
there are few and at other times there are great quantities of masto- 
don and rhinoceros teeth and bones of other mammals, similar in 
some respects to those at Eppelsheim in Germany. 2 Large cetacean 
bones and teeth of Charcharodon and Oxychina are also found. There 
is considerable dispute concerning the origin of the fossils and nodules 
in the phosphate beds of the Crag. That most of them are derived 
masses is shown by their worn and rounded condition. Mr. Jenyns 3 
believes that they have come from the London Clay, and in support of 
this view he calls attention to the similarity of the nodules of the two 
formations. Professor Prestwich 4 thinks that most, if not all, of the 
nodules of the Red Crag came from the Coralline Crag. 
The phosphate deposits of Norfolk are few and scattered. Most of 
the phosphatic material from this county is in the form of mastodon, 
elephant, and rhinoceros bones from the forest and elephant beds. None 
of the Crag phosphate beds have proved so valuable as the Cretaceous 
beds. The nodules are harder and more siliceous, making them more 
difficult to grind and less valuable as a soil stimulant when in the un- 
^eol. Mag., London, 1865. 
2 E. Ray Lankester : ibid. ^ 
3 Ibid., vol. 3, 1866. 
4 Quart. Jour. Geol. Soc. London, vol. 27, 1871, 
(569) 
