244 bulletin: museum of comparative zoology. 



This is natural, for we find on the ledges of the Bermudas mainly seo- 

 lian rock masses readily crumbling to pieces, a thin coral belt, and but 

 little solid material to be shaped into boulders by the sea, and similar 

 to that of reefs studded with massive corals and Madrepores, which are 

 usually crowded with boring Annelids, Sponges, and Mollusks, and which 

 thrive in such localities, but find nothing to feed upon in the seolian 

 rocks forming the base of the ledges of the Bermudas, or in the seolian 

 sand flats, the bottom of which is constantly kept in movement. One 

 finds only occasionally on the beaches of the south shore very limited 

 deposits of flattened pebbles composed of corals, fragments of seolian 

 ledges, and shells of Nassa. 



We can readily follow off the north shore of St. George the transition 

 of the seolian shore ledges into mushroom ledges, or other patches gradu- 

 ally becoiuiug coated with coral growths as they come nearer the main 

 channel into deeper water towards Murray Anchorage. We find here also 

 a few serpuline atolls and fragments of vertical walls protected by Algse 

 or other growths. Sargassum, Algse, and Corallines are especially abun- 

 dant on the inside ledges. 



The ledges I have examined immediately north of the main channel, 

 the southernmost patches of the connecting ledges, all present a very sim- 

 ilar structure. They are deeply eroded on the sides and surface. Some- 

 times one side drops nearly vertically from a depth of two to three feet 

 at low water to six or seven fathoms. The top is more or less flat, re- 

 sembling the ledges near shore, and differing from them only in being cov- 

 ered by a thick growth of Algse and Corallines, which protects their sharp 

 edges and ridges from the effects of the sea. The other faces are more 

 or less sloping, dropping in steps much as the shore cliffs do, and they 

 are more or less undermined and honeycombed. One can sometimes trace 

 what may perhaps have been the low-water shelf of- the ledge before 

 the subsidence had reached its present height, when it was a part of 

 the old shore line cliff, or one of the outlying rocks or islets. 



On the Devil's Flats there are large patches which have in some cases 

 been covered with bank sand, leaving the seolian rocks exposed only on 

 the outer edges, where they are covered with the usual coral growth. 

 In Port Royal Bay, in Great Sound, and in Hamilton Harbor there are 

 many rocky patches rising above the sandy bottom on which Oculina 1 are 

 growing. Along the north shore the rocks are generally thoroughly hon- 

 eycombed immediately above high-water mark; between that and low- 

 water mark they show signs of abrasion and of the solvent action of the 

 sea. The low shore cliffs usually extend from low-water mark outwards 



