A. EF. Verrill—The Bermuda Islands; Geology. 151 
irregular branched burrows of all sizes, finally reducing the coral, 
shell, or even hard limestones, to a mere honeycomb, easily crumbled 
by the waves. They mostly belong to the genus Cliona. One such 
species (C. sulphurea), common on the American coast, from Cape 
Cod to Florida, is famous for its destructive borings not only in the 
shells of oysters, etc., but even in hard marble. 
The related Bermuda sponges have not yet been determined spe- 
cifically, but they are abundant and destructive. 
One of the common reef dwelling sea-urchins (Hehinometra sub- 
angularis, pl. xxxiv, A, has the remarkable habit of forming cavities 
or holes for itself in the solid limestones. Even when it becomes 3 
to 4 inches in diameter the holes just fit its form. 
23, Modern Sand Dunes and Peat Bogs. 
In recent times the activity of the drifting sands has been quite 
variable, depending mainly on the effects of the vegetation that 
borders and encroaches upon the dunes. 
It is singular that none of the early settlers, who wrote such full 
descriptions of most of the other features of Bermuda, say anything 
definite about the drifting sands, which later became a conspicuous 
feature. Neither are areas of barren sands indicated on the early 
maps of Norwood (1626-1663). Though there is mention of some 
barren sandy lands on Ireland Island in the early records,* the dis- 
trict about Tucker’s Town was cultivated, and from the records 
appears to have been fertile, for it is mentioned that Governor 
Tucker (1616) planted figs and pomegranates there. 
Therefore it is probable that at the time of the first settlement of 
the islands (1611) the native vegetation, especially the cedars, had 
so fully covered the soil that the sands no longer drifted to any great 
extent, except close to the shores, and so did not attract attention. 
At the time when Lieut. Nelson wrote (1833-37) the drifting sands 
had attained considerable importance, and he mentions that the drift- 
ing, in the vicinity of Elbow Bay, had begun about 70 years previ- 
ously (about 1763), and at Tucker’s Town about 1773. His account 
is as follows:— 
“The proprietor of the principal part of the land of this bay, the 
venerable Captain Lightbourne, remembers an attempt about seventy 
years ago, when the inhabitants expected an attack from the French 
and Spaniards, to form a breastwork along the sand hills which 
* See these Trans., vol. xi, pp. 476-479 ; ‘‘ The Bermuda Islands,” pp. 64-67. 
