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 tlie island, 

 the continuation of the deep bay. South of the deep hay 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, Avhich 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-flve 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 volcanic 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 

 volcanic 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 soutli, while on the west there is an 

 entrance to Herald Sound (the lagoon of the southwest side of the 

 island) near its northern extremity. 



