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Show 524 LETTER FROM COMMANDER W. E. COOKSON', R.N. L*June ^> margin of the plates of the carapace quite sharply defined as in the young tortoises (which it resembled in shape), whereas in all the full-grown tortoises we had hitherto seen these lines were almost entirely gone. It was at this spot that our guide found, a few months before our visit, the largest tortoise that he had seen for the last fifteen years ; he estimated its weight at about 400 lb. " I have already mentioned that the shell of this large tortoise was so decayed that I did not take it on board; but I took some measurements of it, and am satisfied from these and its shape that the animal had the characteristics I have just described. The epidermoid layer of the shell had for the most part come away; but where fragments were left, the marginal lines of the plates showed quite distinctly. I suppose that abundance or variety of food would be sufficient to produce this difference of appearance in the tortoises from different localities in Albemarle Island, this part of the island, the S.W. end, having a comparatively luxuriant vegetation, whereas the neighbourhood of Tagus Cove is described by Mr. Darwin as being 'miserably sterile;' but it is a point not to be overlooked that these two localities are separated by a coast-line of 70 miles, and that between them lie three of the highest volcanic peaks of the whole group, one if not two of which have been active until quite recently ; and from the flanks of all three streams of black lava descend, each several miles in width. Again, the most northern of these craters is situated almost in the centre of the narrowest part of the island, just a little to the north of Perry Isthmus, and sends down its black streams in all directions; so that this part of the island is exactly like Narborough Island opposite, which is described as 'a great volcano, whose base is surrounded by an extensive field of lava; it is utterly barren and desolate.' I think one may conclude that these lava streams are quite impassable to the tortoises, and that, as far as these creatures are concerned, the north and south ends of the island are as effectually separated as they would be by a channel of 40 or 50 miles of deep water. " With regard to the greatly reduced numbers of these animals in most of the islands, and probable extinction in others, it is known that Charles and Chatham Islands have been inhabited for forty years, which fully accounts for the extinction of the tortoises in these islands, as they have always been eagerly sought for, the oil made from their fat being very valuable and their flesh much esteemed. Their habit of paying periodical visits to their watering- places, and the very plain tracks which they make through the bush or high grass, lead to their easy discovery. The track of a large tortoise is exactly that which a cart with very broad wheels and low body would make drawn over similar ground: the feet make a trail such as the wheels would leave; and between the ' ruts' the grass and low bushes are flattened down by the animal as they would be by the body of the cart. Hood Island never, I believe, had great numbers on it; but James and Indefatigable Islands, where they were at one time so numerous and are |