AGASSIZ: LETTERS TO THE HON. GEORGE M. BOWERS. 75 



of tho line to Manga Reva the hauls were remarkably rich as long as we 

 remained within the influence of the western extension of the Humboldt 

 current, and as long as there poured from the surface masses of the 

 Radiolarians, Diatoms, and Globigerinae living at or near the surface. 

 Some of the hauls were remarkable for the number of deep-sea Holo- 

 thurians and siliceous Sponges. Among the former I may mention a 

 huge Psychropotes, 55 c. m. long. 



As "we passed south and gradually drew out of the influence of the 

 western current, we entered the same barren region we passed through 

 to the eastward when going to and from Easter Island. By the time 

 we reached latitude 15° S., the hauls became quite poor, and this barren 

 bottom district extended to within a short distance of Manga Eeva ; 

 corresponding to it near the surface we found a most meagre pelagic 

 fauna, both at the surface and down to 300 fathoms — so poor that 

 it could attbrd but little food to the few species, if any, living on the 

 bottom in that region. 



We arrived at Manga Reva on the 27th of January and found our 

 collier awaiting our arrival. 



While at anchor in Port Rikitea, we examined Manga Reva, the prin- 

 cipal island of the Gambler group, from its central ridge on the pass 

 leading from Rikitea to Kirimiro on the west side of Manga Reva, as 

 well as from the pass leading to Taku. On both these passes we ob- 

 tained excellent views of the "barrier reef" to the west, north, and east 

 of the Gambler Islands, and we could trace in the panorama before us 

 the western reef extending in a northeasterly direction parallel to the 

 general trend of Manga Reva Island for a distance of about 5i miles. 



From the northern horn to nearly opposite Kirimiro Bay the barrier 

 reef has only three small islets. It is narrow, of uniform width (about 

 ^ of a mile), plainly defined, submerged in places, and passing north 

 bounds a large noi'thern bight dotted with numerous interior coral 

 patches from a quarter of a mile to a mile in diameter or length, witli 

 from 7 to 11 fathoms. The southern part of the western barrier lagoon 

 ofl' Manga Reva is irregularly dotted with many small patches of reef, 

 with an occasional deep hole near Manga Reva Island of from 15 to 20 

 fathoms. 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 deeper channel of from 4 to 6 fathoms, which separates the 

 northern and western reef from the great reef flat lying to the south- 

 west of Tara Vai. This flat has a width of nearly 2 miles, it is about 

 4^ miles long, and is marked at its southwest extremity by a series of 



