59 



either perfectly distinct over large areas, so as to render 

 their identity certain, or, especially in the case of the blocks 

 which are still exposed to wave action, worn away, or con- 

 cealed by a crystalline incrustation. Imbedded in cavities 

 in the Porites, once bored and occupied by the living mollusc 

 animal, are immense numbers of the shells of the lithodomous 

 Venerupis macrophi/lla^ which abounds on the living reef at 

 the present day. The Porifcs are frequently capped by 

 Afitneaiis, which are also fi)und firmly fixed to their lateral 

 aspect. Less commonly they are iucrusted with Mceandriiins 

 {C(florin), which, like the Aiifi'(Pan-s, also form solid isolated 

 blocks, but of far smaller size than the Porites. The blocks 

 are, for the most part, covered on their upper surface by a 

 crust of thick compact laminated sand-rock, imbedded within 

 which are the shells of mollusca — Cardium, Area, Tttrho, 

 Ceritliian}, Spoi(c'i//NK, &c. I have also found several cara- 

 paces of fossil Crustacea, whose species I am unable to 

 identify. At the commencement of the reef, i.e., at the end 

 nearest to the bungalow, the sand-rock is arranged in a 

 s accession of layers with a dip seawards, and forms an 

 incrusting layer about 8 inches thick. A little further on 

 the reef has a terraced appearance, an upper terrace being 

 formed by sand-rock horizontally stratified, exposed to a 

 height of 18 inches, and supported by underljdng Porites, 

 Adroici, Ca'Iorid, and Tnrhtnaria ; and a lower twrace formed 

 by a flat-topped mass of Porifes, about 9 yards in length, 

 covered with loose sand. Not the least interesting feature 

 of the coral wall is the presence of a bank of Madrepores, 

 extending over a length of 8 yards at a higher level than 

 the Porites, and evidently still placed as they originally 

 grew, their radiating branches spreading outwards from the 

 base, and forming a broad fiat surface, which affords support 

 to a thick superjacent layer of consolidated sand-rock. The 

 maximum height of the Madrepores above the loose shore 

 sand is 18 inches, and they clearly form a portion of a bank, 

 such as may be seen spreading over considerable areas on 

 the living reef on a calm day. 



As one looks out to sea from the Pdmban beach at low 

 water on a breezy day, three distinct zones can be clearly 

 distinguished, viz. : — (1) commencing about three-quarters 

 of a mile from the shore, and extending to the horizon, clear 

 blue water separated by a sharp line of demarcation from 

 (2) a zone discoloured by sediment in suspension carried by 

 the carrent through the Pdmban Pass. This zone, in which 



