GHOGRAPHICAL DISTRIBUTION. 345 
Between Australia and New Caledonia the islands are all 
of coral. The Australian reef extending south to the east 
cape, in latitude 24° S., has already been described. Such 
long reefs on the shores of continents are not common. In 
the case of Australia, the zodphytes are not exposed to the 
destructive agents usual on continental shores, as the land has 
a dry climate, the shores are mostly rocky, and there are no 
streams of any extent emptying into the ocean. The east cape 
is the southern limit, because here the tropical current, owing 
to the direction of the coast above, trends off to the eastward 
of south, away from the land, while a polar current follows up 
the shores from the south as far as this cape. South of this 
cape there are only a few scattered coral zodphytes. 
The Louisiade Group is, as has been shown, a region of 
extensive reefs. 
The Solomon Islands, as far as ascertained, are but spar- 
ingly fringed, except the two westernmost, which have some 
large frmging and barrier reefs, and include also some atolls. 
They are described by Dr. Guppy in the Transactions and 
Proceedings of the Royal Society of Edinburgh, 1884-86. 
North of the Solomon Islands are some large reef islands. 
New Ireland, according to D’Urville, has distant reefs on 
part of its shores. 
The Admiralty Islands, farther west, are enclosed by bar- 
rier reefs, and beyond this group there are a few lagoon 
islands. 
The north side of New Guinea is mostly without coral. 
There are several islands off this coast, which are conical vol- 
canic summits, and one of them, near New Britain, and an- 
other, Vulcano, near longitude 145° E., are in action. 
From the facts thus far detailed, the connection between 
the prevalence or extent of reefs, and the various causes as- 
signed as limiting or promoting their growth, is obvious. 
