PRELIMINARY REPORT. ° 14 
near the land it teaches us nothing of their bathymetrical range, as they 
may 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 from 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 1s 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 fathoms, 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 
