Corals from the China Sea . 355 
to be dead ; but the dredge with swabs attached brought up 
from this bank an abundance of living forms. 
Of the three islets on the Tizard Bank (see PL XII.), that 
named Sand-Kay is the smallest and the most recent ; though 
it has increased in size within the last twenty years, it is still 
only a quarter of a mile in length. The surface is somewhat 
depressed in the centre ; it is entirely composed of sand and 
small coral debris. Surrounding the island is a platform of 
coral-rock half a mile broad, covered generally with sand, but 
here and there with patches of growing coral which increase 
in number as the water becomes deeper, and they grow very 
luxuriantly amongst the breakers on the outer edge of the 
platform both next the sea and next the lagoon. Just below 
high-water mark there are parallel lines of hard solid rock 
formed by coral debris and sand cemented together, and a 
reef at a depth of 5 fathoms extends uninterruptedly to the 
westward for a distance of 4 miles. 
The islet of Nam - Yit is rather larger than Sand-Kay ; its 
highest part is not more than 12 feet above high water, and 
in bad weather the waves, according to the natives, break all 
over it. It is well covered with small trees, and the surface- 
soil is therefore of a brown and earthy character ; beneath 
this is a conglomerate of sand and small coral ddbris. A well, 
6 feet deep, passed through loose sandy rock. 
The striking parallel lines of cement-rock are well marked 
on both sides of this island, more particularly on the south or 
weather side ; they have an apparent dip of about 60° from 
the centre, one layer superimposed on the other. This islet 
is likewise surrounded by an extensive shore-platform with 
isolated rocks at its edge, and at its northern end there are 
sand-banks forming horn-shaped prolongations, which partially 
inclose a small lagoon ; on the open side of this, facing the 
lagoon, there are many rocks just below the surface. 
Itu-Aba , the largest islet, is three quarters of a mile in 
length and covered with large trees of considerable age ; it is 
similarly surrounded by a shallow-water platform. Outside 
this, in 6 fathoms water, the number of living corals was 
found by the diver to be much fewer than elsewhere ; but 
from the reef, in 21 fathoms water, several massive specimens 
were obtained, and a rich variety of species was found on the 
lagoon side of the reef. 
A comparison of the sections (PI. XIII.) taken across diffe- 
rent portions of the Tizard Bank shows very great similarity in 
the form and slope of the bank throughout. Thus in all, 
with the exception of section C near Nam-Yit, there is a broad 
plateau sloping very gradually to a depth of 10-12 fathoms, 
