MAKEMO. 103 



erate, resting upon a pedestal of old ledge rising above the general level of 

 the outer platform (PI. 65, fig. 1). The conglomerate ledge at the foot of 

 the beach only exposes here and there the old ledge rock at its base, or it is 

 seen occasionally cropping out as an outlier in the midst of the conglom- 

 erate bed covering its inner face. 



The reef flat near Makemo Pass is not very wide (PI. 59, fig. 2), 

 and pitches quite steeply towards the high many-colored Nullipore edge, 

 which in many places must be fully three feet higher than the reef flat 

 (Pis. 60, fig. 2 ; 62 ; 63, fig. 1). For a distance of nearly twelve miles the 

 reef flat cannot be more than 50 to 70 feet in width, and there is, as at 

 the northwest point, parallel to the shore line, a deep sink ditch, between the 

 outer raised edge of the reef flat and the line of old ledge outcroppings 

 which run out at right angles to the beach (PI. 62, fig. 2). There is a 

 high coral shingle beach at the back of the beach rock conglomerate, made 

 up of recent coral heads and fragments of old ledge, which extends at the 

 foot of the shingle beach in more or less broken stretclies, separated by out- 

 crops of the old ledge rising above this recent conglomerate. Innumerable 

 pools are left at low tide along the slope of the reef flat (Pis. 59, 60, 62, 63), 

 filled with Holothurians, sea urchins (Hipponoe), covered with fragments of 

 dead Nullipores, or corallines, with others crowded with Echinometrae ; 

 black Diadematidai and Echinothrix are sheltered under projections of the 

 ledge or in pools protected by boulders. It is difficult to see how these 

 black Echinoderms have derived any advantage from living on this outer 

 reef flat, where they stand in nearly as strong a contrast on the light yellow 

 rock flat, as they do in the interior of the lagoon, against the white Nullipore 

 and coral sand upon which they equally congregate. 



Fragments of broken corals, ground or worn into the shape of flat or 

 rounded pebbles of all sizes, are thrown in the cracks and between the 

 boulders of the conglomerate or old ledge rock, and gradually become 

 cemented together, forming a coar.«e puddingstone, composed of all the 

 various sorts of materials which go to make up the sea face of a coral 

 reef (PI. 65, fig. 2). 



The beach near the entrance to Makemo on the northeast side is a high 

 coral shingle beach, fully 14 feet in height. Much of the shingle is thrown 



