222 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



worn them into the varied forms they have assumed, either along the 

 more exposed shores or in the sheltered bays and inlets and sounds. 

 Some of the seolian pinnacles oft* Castle Harbor have assumed the most 

 fantastic shapes, due to the combined action of the weather and of the 

 solvent and wearing action of the sea and rain. 



Sir Wyville Thomson r has also given an excellent account of the 

 general characteristics of the seolian formation. Heilprin has called 

 attention to the comparatively insignificant part which corals play in 

 the supply of the material which has gone to form the seolian hills of 

 the Bermudas, and which, as in the Bahamas, is made up of many other 

 organisms. Among them Nullipores, Corallines, broken shells, and 

 Millepores take a most important place. In some localities, where the 

 seolian rocks have not become well indurated, it is not infrequent to 

 have secondary dunes formed from the sand derived from the breaking 

 down of one of the softer cliffs, the dunes covering to a certain extent 

 the older seolian hills, much as the seolian sand of the south coast climbs 

 over the faces of the older hills. 



The fine coral sand, which is so often spoken of as washed up on the 

 shores by the sea, 2 is not, strictly speaking, coral sand, but is primarily 

 composed of fine sand derived from decomposed seolian rock. This ma- 

 terial is derived from the disintegration of the shore cliff ledges, and 

 from that pounded off by the sea from the outer reef ledges, together 

 with the broken shells of the mollusks living upon the flats and the 

 small amount of material supplied by the breaking up of the massive 

 corals and Gorgonians forming the coral growth upon the ledges, the 

 ledges themselves consisting of seolian rock covered by Alga?, Corallines, 

 Serpulse, and Millepores. On the south shore this fine sand is blown 

 far inland, forming dunes which cover extensive tracts; 3 at Middleton 

 Bay beach they run up over the surfaces of the older solidified dunes, 

 and reach to a height of over one hundred feet from high-water mark, 

 encroaching upon the vegetation near the lee summit of the saddle 

 through which they are blown. A row of small dunes has formed on 

 the edge of the beach south of Whale Bay ; a larger dune has also been 

 piled up inland within the line of the beach dunes, extending over an 

 older but smaller solidified dune (seolian hill); just as the beach sands 

 at Elbow Beach (Plates XL, XII.) have run to a height of more than one 

 hundred feet, although here the sand dunes do not extend as far inland. 



i Voyage of H. M. S. "Challenger," The Atlantic, I. 310. 



2 Ibid., I. 307. 



3 See the excellent accounts of the dunes by Thomson, Ibid., 312. 



