PRELIMINARY REPORT. 11 



near the land it teaches us nothing of their bathjmetrical range, as they 

 nia}^ occasionally wander off miles by being carried seaward by currents 

 and drop off into deep water along continental slopes. 



Unfortunately, the marked paucity of pelagic animal life in the Pacific 

 makes it well-nigh impossible to obtain data for their bathymetrical dis- 

 tribution with the limited information we have. 



On our way to Tahiti fi-om the Marquesas we stopped a few days to 

 examine the westernmost atolls of the Paumotus. After striking Ahii we 

 made for Rangiroa, the largest atoll of the Paumotu Group. Skirting the 

 northern shore from a point a little west of Tiputa Pass, we entered the 

 lagoon through Avatoru Pass, anchoring off the village. This pass is quite 

 narrow, with a strong current running out the greater part of the time, 

 especially in easterly winds. It varies in depth between nine and ten 

 fathoms, shoaling near the inner entrance to about three and one half 

 fathoms, and deepening again to six or seven fathoms, and gradually 

 passing into fifteen to seventeen ftithoms, which is the average depth of 

 the lagoon from Avatoru Pass across to the south or weather shore, a 

 distance of about thirteen miles. 



We made an examination of the northern side of the lagoon between 

 Avatoru and Tiputa Passes. The lagoon beach of the northern shore is 

 quite steep, and is composed of moderately coarse broken coral sand at 

 the base, and of larger fragments of corals along the upper face, which 

 is about 5 to 6 feet above high-water mark. These coral fragments are 

 derived in part from the corals living on the lagoon face of the northern 

 shore, and in part of fragments broken by the waves from somewhat 

 below the low-water mark. The ledge which underlies the beach crops 

 out at many places on the lagoon side of the northern land-rim ; we traced 

 it also along the shores of Avatoru Pass, and specially about half-way 

 between Avatoru and Tiputa Passes across the narrow northern land-rim. 

 It crops out also at various points between these passes in the narrow cuts 

 which divide this part of the northern land-rim of the lagoon into a 

 number of smaller islands. These secondary passes leave exposed the 

 underlying ledge, full of fossil corals. In some cases these secondary passes 

 leave a clear channel extending across from the lagoon to the northern 



