434 Rev. R. Aahington Bullen — 



Sir Wyville Thomson ' described an encroachment of sand at Elbow 

 Bay, to which lie applied the name of sand 'glacier' (July, 1873). 

 He describes the steady progress of this destructive invasion, covering 

 cultivated land, overwhelming a house, and advancing through a wood 

 of 'cedars' (Juniperus Bermudiana, L.). Since 1873, however, this 

 sand 'glacier' has ceased to advance landward. Various plants, such 

 as the grape-mangrove ( Coccolaba uvifera, L.), the seaside vine (Ipomcea 

 pes-caprce, Sweet), the bay-bean vine (Canavalia obtusifolia, D. C), 

 burr-grass (Cenchrus tribuloides, L.), and crab-grass (Stenotaphrum 

 Americanum, Schr. = S. glabrum of Lefroy 3 ), have 'anchored' the 

 sand, so that it is no longer a menace. Sir Wyville Thomson writes 

 of 'coral' sand in this account and elsewhere: as a matter of fact, 

 there is no such thing as coral-sand in Bermuda ; the present beaches 

 are not indebted to coral for their materials, but to various marine 

 molluscs, corallines, algse, serpulae, Poraminifera, the tests of echini, 

 Crustacea, etc. ; coral is generally conspicuously absent. 



The matei'ial that constitutes the present shore sand is washed in 

 from comparatively shallow depths, whereas coral lives at depths 

 of "from 5 to 6 fathoms on the inner edge of the flats to the outer 

 limits, the beginning of the broken ground, the corals extending to 

 8 or 10 fathoms on the southern faces of the flats". 3 He also says : 

 " The Bermudian reef corals are, like the Bahama reefs, submerged, 

 rarely come to the surface, and haVe not supplied any considerable 

 part of the material which has gone to build up an extent of land 

 either in the Bahamas or Bermudas." This, any field geologist 

 would corroborate. 



The marine mollusca that contribute to the present shell-sand of 

 the recent beach are represented by the following genera : Area, 

 Barbatia, Bulla, Callista, Cardium, Cerithium, Columbella, Conus, 

 Cylichna, Cyphosoma, Cypraa, Dentalium, Biplodonta, Eulima, 

 Fissurella, Glycimeris, Melampus, Murex, Nassa, Nerita, Olivella, 

 Patella, Pecten, Rissoa, Spirula, Spo7idyhis, Trivia, Vermetus. There 

 are probably many others, but these are in my own cabinet. 4 



It would extend these notes unduly if I were to describe the 

 swamps, which, though not very extensive, are of great depth, and 

 may go back to very early times, but as they have not been explored 

 downwards there is but little known with sufficient exactness for any 

 lengthy geological report. Suffice it to say that Governor Lefroy 

 found the depth of the peat in Pembroke marsh in 1872 to be 42 feet. 



IY. The Sekpuline 'Atolls' ok, 'Boilers'. 



The term here used refers to the round, or horseshoe, or S-shaped, 

 or compound-shaped reef edges which occur on the south shore 

 (PL XX, Fig. 2). " They are, perhaps, the most interesting 

 structures in the Bermudas. They . . . constitute miniature atolls 

 and barrier and fringing reefs, apparently formed by the growth of 

 serpulse. While serpulae undoubtedly cover a great part of the 



1 Voyage of the " Challenger ", vol. i, p. 310, figs. 74-6. 



2 Lefroy, Botany of Bermuda, 1874. 



3 Agassiz, A Visit to the Bermudas in 1894, pp. 237, 243. 



4 Through the kindness of Miss Aimee Kempe, of Warwick parish. 



