A. E. Verrill— The Bermuda Islands; Geology. 73 
Walsingham limestone, while others only reach its upper surface, or 
fail of that even. The hardness of the rock seemed to have had no 
influence. They may have been formed before it was hardened. 
Above the red clay surface there is here a deposit of beach-rock 
(c), three or four feet thick in some places, and containing many 
marine shells. The latter is irregularly laminated, and locally 
variable in thickness and character. It appears to have been a true 
marine deposit, formed below high-water mark, but now elevated 
five to eight feet above it. 
This is overlaid, along most of this exposure, by a layer of drift- 
sand (d) which is only slightly consolidated and friable to the touch, 
especially in its upper part. Hence the storm, referred to above, 
readily cut it out into the cavernous or oven-like places, shown in 
some of the plates, under the overlying strata (e) of later olian 
limestones, which are here well indurated. The unconsolidated 
layers contained, in the lower part, some fragments of marine shells. 
There were mostly small valves of Mytilus and other light bivalves, 
easily drifted by the wind, but in its upper part it contained the 
land snail, Pectlozonites Bermudensis (plate xxvii), which is still 
living, and there were no extinct forms found with it. 
Following this exposure westward the unconsolidated beds soon 
disappear or become so consolidated that they cannot be distin- 
guished from the overlying eolian limestones, which continue. The 
beach-rock also disappears locally, so that the upper xolian lime- 
stones may rest directly on the Walsingham limestone, though 
unconformably. 
The arrangement of this series of rocks is almost the same at 
various other places, as at Devonshire Bay. It was observed there, 
both by Rice (1884) and Stevenson (1897, p. 105), underlying the 
beach-rocks containing marine shells,. Professor Stevenson’s descrip- 
tion will be quoted below, under beach-rocks. 
It happens that the hard limestones of this formation occur along 
much of the southern coast of the island, just above sea-level ; 
between tides; or more or less submerged. In many places the 
strata lie nearly horizontally, though not always so. In case these 
nearly horizontal, compact beds outcrop between tides, or a little 
below low-water mark, they will resist the erosion of the waves 
much more effectually than the softer overlying limestones of later 
age. Thus they are sure to form, under such conditions, more or 
less extensive “‘ benches” or shelves, between tides or lower down. 
The waves speedily wear away the layers of red clay and the 
