^378 Mr. A. Alcock on the Bathyhial Fishes 



According; to the rescarclies 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 

 cast 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 ofi" the 

 Nicobar- Andaman coasts. The minimum depth yet found on 

 the ridge is 1340 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 Avhich (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. Except in its centre 

 and in its south-western part it is shallow. 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 ofi" 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. Ivi. 

 pt. ii. no. 2, 1887). 



