1912.] R. B. SevMouR-SEWELL: Sur/ace-Living Copepoda. — 351 
South Moscos South Island there is a very definite scouring out of 
the sea bed, the depth here suddenly increasing to over 20 
fathoms. Such a current coming down from the more northerly 
region of the Bay of Bengal would also account for the presence 
in area II of the serial form of Cevalium tripos, a form which, it 
is generally stated, is only found well out to sea and remote from 
any land. 
On the other hand, however, area III would appear to run 
in a direction exactly opposed to such a current, for this area is 
directly continuous with the region at the mouth of Tavoy River. 
There is no doubt that this area is largely influenced by tides, for 
on two occasions the ship while carrying out a line of soundings 
passed xight across this region, and although the net was down 
the whole time, the type of plankton obtained was typically that 
of area II; on both occasions, however, the tide was on the ebb, 
and this would appear to indicate that during the flood tide this 
area is carried up from the south from the region of Tavoy River 
to the east of the South Moscos Islands, and on the ebb tide it 
again recedes, its place being taken by water from area II. 
The variations in the tow-nettings of these four areas were, 
however, not confined merely to the diatom flora; marked differ- 
ences were found to exist regarding the occurrence of various 
species of Copepoda. This was particularly well marked in the 
case of area 1 as compared with the remaining three areas, and 
in the following table I have endeavoured to indicate these differ- 
ences as fully as possible, the frequency or the reverse of several 
species being shown in percentages of the total Copepod catch. 
Areas II and III 
(8 localities). 
Area I 
(5 localities). 
Area IV 
(2 localities). 
CALANIDAE. 
Canthocalanus pauper 
Undinula caroli 
Eucalanus subcrassus 
Acrocalanus 
nts. 
PONTELLIDAE. 
Labidoceva acuta 
| 12°33% in one local-| 
ity: less than 4% | 
in all others. 
Less than 1% in 
all localities. 
66% and 132% 
in two localities: 
less than 2°5% in 
all others. 
longicor- | Less than 1% 
. | From 19°8 to 59% 
in all localities. 
From 6 to 29°5% | From 6 to See 
in 5 of the 8 local- 
ities. 
From. 3 to 16% in | Less than 1%, 
five localities. 
' From 8 to 22% in| 11% in both lo- 
seven localities. calities. 
From 5 to 29°5% 
2% in both Iocal- 
in six localities. | 1 
ities. 
From 5°4 to 8% in | Less than As 
three localities: | 
less than 3% in | 
all others. 
