36 
CORALLINE CRAG. 
buried cliff of' Coralline Crag at Tattingstone will be found in 
the Chapter on the Red Crag (p. 89). 
This completes the description of the sections which have been 
or are now visible of the Coralline Crag. It will be seen that the 
deposit consists essentially of calcareous sand, mainly composed of 
shells or Bryozoa; the upper portion having been cemented into 
soft limestone of similar origin, but having the aragonite fossils 
dissolved and the carbonate of lime re-deposited in the form of a 
cement, or as streaks of tufa. A few thin seams of marl, pale- 
green when wet but drying nearly white, have been found, but 
most of the so-called marl is merely wet calcareous sand. When 
a portion of the Coralline Crag is treated with acid, the calcareous 
constituents are entirely dissolved, and a small but variable residue 
is left composed of fine siliceous sand full of grains of glauconite, 
exactly like the Diestian sands of Antwerp. 
A few phosphatic nodules, unlike those of the bone-beds and 
apparently foJined in place, occur scattered through the Coralline 
Crag. Otherwise the lower portion seems to be in the condition 
in which it was laid down on the floor of the sea as a loose sand, 
or as a soft rock sufficiently consolidated to support branching 
Bryozoa and Corals. The contemporaneous consolidation of the 
sea-bed does not appear to take place in our latitudes at the pre¬ 
sent day ; but in warmer seas it is common, and on the shores of 
the Gulf of Lyons I have picked up slabs of sub-littoral sands 
which had evidently consolidated quite recently in shallow water, 
and had been torn up by some storm. 
The whole of the Coralline Crag is more or less current-bedded, 
sometimes at high angles, such as may be seen in an ordinary 
sandstone, sometimes in flowing curves. I have been unable to 
recognize in Prof. Prestwich’s division e a single stratum un¬ 
affected by this current-bedding, for at Broom Hill—one of the 
two localities given for this horizon—the sketch (Fig. 4, p. 30) 
shows this structure distinctly throughout. I therefore spent 
a good deal of time in getting the exact inclination of the current¬ 
bedding in the Broom Hill Pit, for if this stratum had been laid 
down at a depth beyond the reach of currents, it would betoken 
deeper water than any other part of the formation ; all the rest 
of the Coralline Crag is unmistakably false-bedded. The other 
locality where Prof. Prestwich considers horizontally stratified 
Crag to be present is at Sutton ; but here, though the currents 
seem to have been gentle, it is interesting to note how constantly 
the straight cylindrical branches of Salicornaria have been rolled 
and waterworn. Tiie rolled condition of small cylindrical Bryozoa 
and the unworn state of the ramose or heavier forms affords a 
good indication of the strength of the marine current, for it shows 
that the force must have been sufficient to move the smaller 
particles or sand, except where these happened to be immediately 
cemented by carbonate of lime, or bound together by organic 
growth. This contemporaneous binding together of the particles 
is, I believe, the cause of the occasional local absence of current¬ 
bedding and of the undisturbed state of the fossils—the currents 
