INTRODUCTION. v 
Tue Rep Crag. 
1. Its structure.—The physical structure of the Red Crag is unlike that of any other 
formation known to us, ancient or modern. The more considerable portion of it is 
formed of a succession of beds, varying from two or three, to nearly twenty feet in 
thickness, each of which consists of lamine of sand and shells, inclined at a high degree 
to the horizon. The laminz planes of each bed form an angle with those of the other beds 
above and beneath them; and at the base of each bed they change into a slight curl.’ 
This structure is altogether different from the well known one of false bedding, which 
also exists in some parts of the Red Crag, especially in that under which the phosphatic 
nodules are worked, and the two forms of bedding pass more or less into each other. 
This oblique lamination may be traced (as, for instance, in Bawdsey Cliff) for a consider- 
OBLIQUE RED CRAG IN BAWDSEY CLIFF. 
The oblique bedded crag appearing above the Talus is nearly twenty 
feet in thickness. 
able distance in a constant manner, without shading off into horizontal stratification 
or passing into false bedding. If we examine a section of any beach or foreshore 
(at right angles to the line of the shore) we shall find it presents exactly this 
describes eighteen species, of which only five are recognised as living, viz. Cythere punctata, C. sublacunosa, 
C. trachypora, Cythereis ceratoptera, and C. tamarindus ; the first and fourth of which are species of the 
British coasts, the third and fourth of the Norwegian coast, and the fifth an Atlantic form. Of the Polyzoa 
their describer Mr. Busk says, in a letter to the author of the ‘Crag Mollusca, “ Judging from the habits of 
existing forms, those of the Crag may have lived at any depth from the surface downwards,” to which we 
may add that the rock bed made up of the remains of Polyzoa is very false-bedded, which is indicative of 
the reverse of deep water. 
1 Something approaching this oblique lamination may be seen in the Great Oolite of the Great Northern 
Railway cuttings near Grantham, and on the Yorkshire coast south of Scarborough. 
