78 PUOFESSOi; T. W. EDdKAYORTH DAVID AND Mil. C4. SWEET. 



Hygroscopic moisture -09 



Loss on io-nition 2 '2 9 



SiOo 66-50 



Fe^Og 3-21 



AI0O3 16-84 



CaO 3-0.-3 



MgO 1-03 



K.O 5-44 



NaoO 2-53 



P,0, trace 



100-96 



A i)artial analysis of another pel)l)le of a darker shade gave 60"-37 of SiO.,. 



Tlie general appearance of the Hiui-icane Bank facing the ocean, as well as of the 

 reef platform at low tide, is shown on Plate E, the lower figin'e giving the living 

 Liihothamnion zone, O.L.IO, just awash at low tide, and ne.vt inshore the zone of 

 dead Lithot/iarniiion, ()..'>, succeeded hy the old hreccia sheet, and surmounted l)y the 

 Hurricane Bank. 



The deposit ().3 may he defined as a zone of dead Lithoth amnion and foraiui- 

 niferal rock, more or less of the natm-e of a hreccia, with a smooth or slightly 

 mammillated surface. It lies next inshore to the livino' LlthothanDiion zone of the 

 ocean platform, and is carpeted in ])laces Avith suiall green algse, rejjlaced occasionally, 

 as at Funamanu, hy ochreons alga\ Ju addition to Lifhothamniov, PoJytrema plamim 

 has played an important part in building this stratuui. A reference to Plate 17, 

 Section on line (J-1), hy Mr. G. H. Halligax. sliows the general relation of this cnist 

 of dead Lithoth amnio a, Pohjtrema, Carpentevia, &c. . to the old llehopora cferuleo. 

 reef, O.L.I. This section mav he taken as a tv])e of what ohtaiiis elsewhere on the 

 eastern rim of the atoll. 



It will he noticed that towards the ocean edu'e of the ().3 zone the deposit lise-J 

 first, then falls over so as to form a low rim ahont 6 to 7 inches above the general level 

 of the small flat inside it. This fiat, bounded seawards by the rim, is occupied 

 1)}' a series of long shallow pools at low tide. Accurate levels, taken with a 12-inch 

 dumpy level, by Mr. HALLr(4AN, show that the top of this rim is 2-82 feet above 

 low water, whereas the bottom of the flat inside it is oidy about 2*22 feet above 

 the same datum. A glance at the deposit which comes next outside, O.L.IO, the 

 living Lithothamnion zone, shows a repetition of the shallow flat and i-aised rim, the 

 levels in this case being respectively 1 '21 and 2-22 I'eet al)ove low water. 



We have formed two conclusions from this: — (1) That the rim of 0.3 represents 

 the former outermost rim of the reef platform at low tide, a position analogous to that 

 now occupied by the rim of O.L.IO, and consequently that the edge of the reef plat- 

 form since the death of the Lilhot/iamiiion and other organisms forming 0.3 has 



