20 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
width extend towards the northeast extremity of the outer reef. The 
outer reef flats are narrow, and run in a southerly direction, forming an 
elbow opposite the eastern point of the island at a distance of from one 
to two miles, and enclosing the lagoon off the eastern face of the island, 
the continuation of the deep bay. South of the deep bay the outer reef 
nearly connects with the edging reef of the island, leaving a passage 
DEEP BAY, EAST FACE OF MOALA. 
across the outer reef about a mile in width, the southern horn of which 
extends about three miles to the south, then in a westerly direction, 
then north until it strikes spurs of the fringing reef on the northwestern 
coast of the island, where the outer reef forms in connection with the 
fringing reef a series of reef flats full of coral patches and heads. The 
lagoon to the southwest of the island is also full of coral patches and 
heads, some of them of considerable size, which extend to Herald Road- 
stead, the northeastern part of the lagoon, which alone is comparatively 
free from obstructions. Owing to the presence of so many patches and 
heads the depth in the lagoon is most irregular. In Herald Sound it is 
as great as twenty-five fathoms, and somewhat less off the southwest 
and northern coasts. The characteristic heads which crop out from 
the shore at so many points are well illustrated by the heads composed 
of voleanic rocks which form the spit protecting the anchorage to the 
west of Naroi village, on the north shore of the island. Wherever we 
dredged we found that the bottom inside the lagoon consisted of fine 
voleanic mud mixed with coral ooze and broken shells. , 
There are two entrances to the lagoon on the east face, one opposite 
the deep bay, the other to the south, while on the west there is an 
entrance to Herald Sound (the lagoon of the southwest side of the 
island) near its northern extremity. 
