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Show 440 LT.-COL. H. H. GODWIN-AUSTEN ON THE LAND- [May 21, and in tbe 'Journal' of the same Society, 1893, has given an account of bis collections principally of the flora of Narcondam and Barren Island ; although be mentions the presence of land-crabs, spiders, scorpions, and ants on Narcondatn, no Mollusca are recorded. All the above-mentioned air-breathers, it is quite possible, might reach this island on trees floated off from the Andamans during the monsoon which blows so long from that direction, and they would all have a better chance of survival in sea-water than Land- Mollusca, and might be carried for long distances inside the joints of the bamboos and large grasses. Dr. Prain publishes two good maps of the Andaman Group, and the lines of soundings ranging from 100 to 2000 fathoms are shown. These point out very clearly, as he shows, that the Andaman Sea, as a physical feature, is distinct from the great oceanic-depression outside, which he terms the sea of Bengal, down to about 5° north. These cootour-lines of soundings also show how the western face of the Andaman-Nicobar line of elevation suddenly descends into the deep water of about 10,500 feet in a distance of from 60 to 70 miles, and this is proportional nearly to the elevation of the Arakan range above the sea, on latitude 22°, near the head of the Bay of Bengal and to its distance from the present sea. The parallel contour-lines of soundings down to tbe 1000-fathoin line extend north up the coast of Arakan, and south close to the islands off the coast of Sumatra, M a s , & c , indicating a former extension of land upon this line. It is said that the Andamans present evidence of recent subsidence1, and these charts of Dr. Prain's show that an elevation of 600 feet in this single group would unite them to Pegu and Arakan, leaving an extremely narrow channel of only 50 fathoms deep south of Preparis. The Nicobars are more isolated, and deep wide channels separate them from the Andamans on one side and Sumatra on the other, which accords with the paucity of Land-Shells common to both, and the presence of a few found in Sumatra. That these islands have been cut off for a considerable period from the adjacent continents and islands is shown not only in tbe specific variation of the molluscan fauna, but equally in the birds by a great number of distinct and peculiar forms. A great deal yet remains to be done: the highest parts of the Nicobars have never been collected on; here we may yet find species identical with those of the Andamans, for many obtained there come from tbe higher elevations, while most of those from tbe Nicobars have been taken near tbe sea-coast; and a few hundred feet of elevation would bring in quite a different set of forms. 1 S. Kurz, ' Report on the Vegetation of the Andaman Islands.' |