378 Mr. A. Aleock on the Bathybial Fishes 
According to the researches of the same observer the 
southern half of the Bay is not a simple basin, for, about 
three and a half degrees west of the Nicobars, running almost 
north and south, a remarkable ridge, which may be fitly 
named, after its discoverer, Carpenter’s Ridge, marks off on 
the south-east, between itself on the one side and the Nicobars 
and South Andamans on the other, a small basin almost 
symmetrical with the Gulf of Manaar on the south-west. 
‘This ridge is well seen on the contour-map (Admin. Rep. 
Mar. Surv. Ind. 1888-89), where the contours up to 1600 
fathoms sweep across the bay in main directions of west and 
east or north-west and south-east, while the contours from 
1700 to 2200 fathoms, within the parallels of 16° to 6° N., 
after taking semicircular curves, with their convexities north- 
wards, across the western half of the bay, run down south- 
wards in deep loops in the eastern half round the ridge, 
turning northwards again to their final convergence off the 
Nicobar-Andaman coasts. ‘The minimum depth yet found on 
the ridge is 1840 fathoms. 
The Andaman Sea is a good deal land-locked. To the 
south it passes into the shallow Straits of Sumatra and to the 
north into the far shallower Gulf of Martaban, which receives 
the River Irrawddi. 
On the west it communicates with the Bay of Bengal by 
three main channels, the shallowest of which (South Preparis 
Channel) to the north is 150 fathoms in depth, the deepest 
being 760 fathoms, between the Nicobars and Sumatra. On 
the east it is crowded with small islands. Iixcept in its centre 
and in its south-western part it is shaliow. So far the 
greatest depths known are in the centre (1200 fathoms), close 
to the east coast of Middle Andaman Island (1159 fathoms, 
bottom-temperature 39°°5 Fahr.) and near the same coast of 
Great Nicobar Island (1284 fathoms). ‘The only specimens 
of the bottom which I have examined are from 1159 and 1130 
fathoms off Middle Andaman Island, and these were dark 
mud, with but little matter of direct organic origin. 
The Gulf of Manaar, between India and Ceylon, commu- 
nicates with the Bay of Bengal by the shallow Palk Strait. 
On the south-east its basin is very abrupt. The greatest 
depth yet found in the more open part of the Gulf is 1466 
fathoms (bottom-temperature 34°°8 Fahr.), and the bottom 
appears to be green mud throughout. It was in this gulf 
that the ‘ Investigator ’ in 1886 trawled some curious baryta- 
nodules (Jones, “On some Nodular Stones obtained off 
Colombo in 675 fathoms,” Journ. As. Soc. Beng. vol. lvi. 
pt. i. no. 2, 1857). 
