238 "ALBATROSS" TKOPICAL PACIFIC EXPEDITION. 



The lagoon is said by Wilkes to be about five fathoms deep, and to have 

 many sand and coral shoals dry at low water. 



Tapeteuea is undoubtedly the summit of a very extensive ridge, as to the 

 south of the charted part of the atoll an extensive reef has been reported 

 by the U. S. S. " Narragansett." 



The northern horn of Tapeteuea^ (Pis. 223; 226, fig. 1) reminds us of 

 the horns of the atoll of Arhno, in the Marshall Islands, where the land rim 

 is flanked on both faces by a fringing reef platform widest on the lee side. 

 The loose material composing the eastern land rim has, as yet, reached only 

 an initial stage of concentration, consisting wholly of small islands, islets, 

 and sand bars. On the northern and southern extremities alone a part of 

 the land rim of the east face is continuous, and has been consolidated 

 into larger islands (PI. 138, fig. 3). 



We came upon Tapeteuea" near the centre of the eastern face of the 

 atoll, where the land rim consists of numerous islands and islets, flanked 

 by low sand beaches (PI. 138, fig. 2) ; many of the islands seem to be 

 connected b}' sand bars. 



On the southern side of Utiroa we saw several artificial mounds, such 

 as we had noticed at the extremity of Arorai. Some of them seemed to be 

 beacons, indicating, perhaps, a canoe passage into the lagoon. But on the 

 western side of the same island occurs a long line of these artificial piles, 

 the object of which is not so apparent, as they merely extend westward into 

 the narrow lagoon on the broad western fringing reef flat. As we steamed 

 along the east side of Tapeteuea (PI. 226, fig. 1), close to the line of 

 breakers, we could see that the various islands and islets to the south of 

 Utiroa are largely sand bars reaching out at right angles to the line of the 

 outer reef platform, the sea face of wliich is flanked with conglomerate 

 beach rock, while the lagoon end of the islands and islets is covered with 

 fine coral sand thrown up by the waves of the lagoon during the prevail- 

 ing trades. These sand bars, according to their size and age, are covered 

 at first by a low growth of bushes, subsequently cocoanut trees find a foot- 

 hold, and eventually cover the greater part of the ridges of the islands. 

 The gaps between the islands and islets appear to be shallow (PI. 138, 



1 H. O. Chart 120. * Ibid. 



