Geology of the Bermudas. 435 



surface of the structures, yet calcareous algae, corallines, barnacles, 

 mussels, and other invertebrates are found to be fully as abundant as 

 the serpulse, which, in many cases, play only a secondary part in the 

 organic covering . . . Before my visit to the Bermudas, I accepted 

 the explanation given by older writers of the mode of formation of the 

 atolls, as due to the accelerated growth of serpulse on the outer rim. 

 I was therefore greatly surprised on hammering at some of these 

 structures to find that the vertical walls were not built up, as is 

 generally believed, of serpuline limestone, but were composed of 

 seolian rock, and to discover that in many cases the elevated rim was 

 protected by the hard ringing crust so characteristic of limestone 

 exposed to the action of the sea, and, further, to find that the coating 

 of serpulse, algas, corallines, and nullipores was quite superficial." 

 Agassiz ' gives good reason for believing that these miniature reefs are 

 caused by the gouging action of the surf on seolian rock, submerged at 

 high tide, but at other times elevated a foot or so above the water, on 

 which the incessant play of the waves has a degrading effect. The 

 growth of serpulse, etc., protects the outer rim, and these interesting 

 structures are the result. 



The serpulse are curiously more abundant on the south ' reefs ' than 

 on the north flats. There this phenomenon is not so well developed ; 

 the surface of the northern ledges are mainly protected by a small 

 species of barnacle, clusters of Mytilus, encrusting nullipores, and 

 a few small species of algse. 2 



Y. The Foraminieera. 



I am indebted to Mr. Richard Holland for the following report on 

 the Foraminifera which I have submitted to him : — 



" Six packets of various kinds of materials were sent to me for 

 examination, namely — 



I. Coarse recent sand from Mermaid's Hole. 



II. Fine recent sand from Long Bay. 



III. Very fine fossil sand from near the Park, St. George's. 



IV. Fine sand, probably from Shelly Bay. 



V. \Fine sandy material collected from the insides of various land shells 

 VI. / from the Paget formation. 



" Specimen I. This might fairly be described as a shelly gravel. It 

 contains no fine material, and is, in fact, too coarse for the occurrence 

 of Foraminiferal debris or even entire Foraminiferal shells. It consists 

 largely of molluscan debris with coarse sponge spicules and other organic 

 remains. 



" Specimen II has a general resemblance to Specimen I, but it is 

 much finer, and includes a great quantity of Foraminiferal debris, 

 rolled and worn Orbiculince and Orbitolites, and numerous complete 

 smaller shells. 



" Both Specimen I and Specimen II are perfectly clean sands, with 

 not the slightest admixture of mud, calcareous or other. 



" Specimen III is a fine sand with a slight admixture of calcareous 



1 Agassiz, A Visit -to the Bermudas in 1894, pp. 264-7, figs. 1-7. Also 

 Nelson, op. cit., p. 116, figs. 11-13. 



2 Agassiz, op. cit., p. 264. 



