8 GEOGRAPHICAL DISTRIBUTION [CHAP. VII 



Letter 384 strange it is, that his view not affording the least explanation 

 of the innumerable adaptations everywhere to be seen 

 apparently does not in the least trouble his mind. One 

 of the most curious cases which he adduces seems to me 

 to be the two allied fresh-water, highly peculiar porpoises 

 in the Ganges and Indus ; and the more distantly allied 

 form of the Amazons. Do you remember his explanation 

 of an arm of the sea becoming cut off, like the Caspian, 

 converted into fresh-water, and then divided into two 

 lakes (by upheaval), giving rise to two great rivers. But 

 no light is thus thrown on the affinity of the Amazon form. 

 I now find from Flower's paper 1 that these fresh-water 

 porpoises form two sub-families, making an extremely 

 isolated and intermediate, very small family. Hence to us 

 they are clearly remnants of a large group ; and I cannot 

 doubt we here have a good instance precisely like that of 

 ganoid fishes, of a large ancient marine group, preserved 

 exclusively in fresh-water, where there has been less 

 competition, and consequently little modification. 2 What 

 a grand fact that is which Miquel gives of the beech not 

 extending beyond the Caucasus, and then reappearing in 

 Japan, like your Himalayan Pmusf and the cedar of 

 Lebanon. I know of nothing that gives one such an idea 

 of the recent mutations in the surface of the land as 

 these living "outlyers." In the geological sense we must, 



1 Zoolog. Trans. VI., 1869, p. 115. The toothed whales are divided 

 into the Physeteridae, the Delphinidas, and the Platanistidas, which latter 

 is placed between the two other families, and is divided into the sub- 

 families Iniinas and Platanistinae. 



2 See Vol. I., p. 143, Letter 95. 



3 For Pinus read Deodar. The essential identity of the deodar and 

 the cedar of Lebanon was pointed out in Hooker's Himalayan Journals 

 in 1854 (Vol. I., p. 257. n). In the Nat. History Review, Jan., 1862, 

 the question is more fully dealt with by him, and the distribution 

 discussed. The nearest point at which cedars occur is the Bulgar-dagh 

 chain of Taurus 250 miles from Lebanon. Under the name of Cedrus 

 atla?itica the tree occurs in mass on the borders of Tunis, and as 

 Deodar it first appears to the east in the cedar forests of Afghanistan. 

 Sir J. D. Hooker supposes that, during a period of greater cold, the cedars 

 on the Taurus and on Lebanon lived many thousand feet nearer the 

 sea-level, and spread much farther to the east, meeting similar belts of 

 trees descending and spreading westward from Afghanistan along the 

 Persian mountains, 



