A. EL. Verrill— The Bermuda Islands; Geology. 69 
building stones. But in many other places these rocks have remained 
friable or soft, with well marked sand-drift structure. In some cases 
they include layers or pockets of imperfectly consolidated, or loose, 
shell-sand. Between the layers of limestone are successive layers of | 
“red-clay,”—a decomposition product, representing ancient soils, 
and often containing numerous extinct land-snails. The red-clay 
may be more or less indurated by the infiltrations of calcite, or 
stalactitic materials, with which, and the shells, it sometimes forms 
a breccia-like reddish mass (fig. 45). The fossil land-snails occur in 
the limestone, whether it be consolidated or friable, but are most 
abundant in those portions connected with the layers of red-clay, 
especially in and just above the latter. 
Most of the larger caverns and sinks, like those of Walsingham 
and vicinity, have been formed in this formation, which seems to 
contain the oldest rocks now exposed to view on the islands, and to 
form the nuclei of the larger hills. It is found at all levels, from 
below low-tide mark to the elevation of 70 feet or more. Its hard 
compact layers, exposed in many places on the south side of the 
main island, just above high-water mark, are those that have been 
called “base rock” by Heilprin, Rice, and others,* and “ the lime- 
stone” by Stevenson, but they are of the same nature as, and essen- 
tially contemporary with, those that occur elsewhere at greater eleva- 
tions, as shown by the overlying red clay and extinct snails. The 
best examples of the so-called molds and casts of “ palmetto stumps ” 
also occur in this formation (see plates xix, xx), showing that the 
latter might have been due to some extinct and unknown plant or 
animal. 
This formation outcrops in numerous places on the ancient Wals- 
ingham property, between Castle Harbor and Harrington Sound, 
hence the name given to it. It seems to form most, if not all, of the 
high neck of land separating those two bodies of water, for it out- 
* Professor Rice, op. cit., p. 9, 1884, stated that the so-called base rock ‘‘ does 
not uniformly underlie the softer rocks, nor is there any evidence that it is older 
than they.” He apparently referred to all the hard limestones of, drift-sand 
origin, near sea-level, taken collectively. Agassiz, 1895, held essentially the 
same view. 
But Stevenson, 1897, claimed that this rock, which he called ‘‘ limestone,” 
represented a distinct formation, underlying the ordinary xolian limestone, 
which he called ‘‘ sandstone.” However, he considered the limestones and red 
clays, containing extinct snails, around Castle Harbor and Harrington Sound, as 
a newer formation, ‘‘The intermediate deposit,” of the same age as the beach- 
limestones. With this conclusion I do not agree. 
