368 Agassis — Albatross Expedition to the Eastern Pacific. 



a mile to a mile in diameter or length, with from 7 to 11 

 fathoms. The southern part of the western barrier lagoon off 

 Manga Reva is irregularly dotted with many small patches of 

 reef, with an occasional deep hole of from 15 to 20 fathoms 

 near Manga Reva Island. From the islet to the west of 

 Kirimiro there are but few coral patches, indicating a reef 

 which dips gradually in a distance of a mile to a deep channel 

 of from 4 to 6 fathoms, which separates the northern and 

 western reef from the great reef Hat lying to the southwest of 

 Tara Vai. This Hat has a width of nearly 2 miles, is about 

 4i miles long, and is marked at its southwest extremity by a 

 series of low islets arranged in a somewhat circular line, 

 formed by three deep bays and spurs from the outer line of 

 islets, as so frequently occurs on a wide reef flat in atolls of 

 the Pacific. 



This part of the reef is called Tokorua. It shelves very 

 gradually from 3-J- to 4 fathoms on the west face to T, and con- 

 nects with the plateau upon which stands Tara Yai and Aga- 

 kanitai. From Tokorua the reef extends in an indefinite 

 narrow ridge 8 miles long, with from 3 to 8 fathoms, in a 

 southeasterly direction. The western edge is steep to, and 

 the eastern face passes gradually into the lagoon, which at 

 that point has a general depth of 8 to 20 fathoms. The deepest 

 part of this region is at the foot of Mt. Mokoto between it and 

 Tara Yai, though Tara Yai is united with Manga Reva Island 

 by a platean varying in depth from 3^ to 4J fathoms. 



At the southeastern point of the reef it passes into a wide 

 plateau with from 9 to 10 or 15 fathoms. This plateau is 

 about 9 miles wide southwest of Tekava. That part of the 

 atoll has not been well surveyed, so that the position of the 

 reef flat has not been ascertained further west on that part of 

 the east face ; but the southeast passage indicates 5-J, 6 and 6-J 

 fathoms, where it probably marks the southwestern extension 

 of the eastern barrier reef, separating the lagoon from the 

 southern plateau to the south of the encircling reef. 



The western face of Manga Reva and of Tara Yai are 

 indented by deep bays, which are formed by spurs running 

 from the central ridge of these islands, the remnants probably 

 of small craters which flanked the large crater, of which 

 Manga Reva forms the western rim and An Kena is the rem- 

 nant of the southeastern edge, the former extension of this 

 rim being indicated by the spits uniting the base of Mt. Duff 

 with Au Kena ; and by the projection of Au Kena towards the 

 outer barrier reef, and of the numerous patches of coral reef 

 off the northeast point of Manga Reva towards the outer line 

 of motus until they almost unite with the barrier reef. 



