„Coralreefs and crustal movements”. 
By W. M. Davis. 
The general nature of the shore line on which reefs occur, 
either fringing reefs alone or fringing reefs in the lagoon of 
an off-shore barrier reef, is of importance. The chief 
point here is: does the land-slope exhibit forms due to erosion, 
such as hills and valleys, and do these forms appear to dip 
below the sea level? If so, the shore line will necessarily 
be irregular, advancing around the outstanding points and 
entering into branching embayments in the valleys. Such a 
shore line clearly indicates submergence after the erosion of 
the hill and valley forms, and before the formation of the 
present reefs. 
It may well happen that since submergence took place, 
the embayed shore line has been modified in two ways. 
First, by the formation of deltas in the bay beads, and in 
this case the line of contact where the land slopes descend 
to the inner border of the delta plains should be noted. 
Second, by cutting cliffs on the headlands: when such cliffs 
are found it is particularly important to enquire if they are 
bordered by a low-tide rock platform, the breadth of which 
is such that the prolongation of the land slope from above 
the top of the cliff would about reach the outer border of 
the rock platform. Such a relation clearly indicates that 
the cliff has been cut by waves at present sea level. Out- 
side of the rock platform a fringing reef very often occurs. 
It sometimes happens, however, that spur-end cliffs descend 
abruptly below sea level and are not fronted by a shallow 
rock platform. In such cases the lagoon outside of the 
fringing reef may have a depth of 10 or 20 fathoms close 
to the land. This relation clearly indicates that the visible 
cliff is only the upper part of a higher cliff, the lower part 
