| OCR Text |
Show 718 SURGEON F. DAY ON THE [Dec. 5, archipelago, down to which point my investigations have more or less been carried on. His limits of this archipelago, lying between Asia and Australia, extend from the Nicobars and the Tenasserim provinces on the west, to the Philippines on the east, thus forming its northern boundary ; whilst the Solomon Islands beyond New Guinea define it on the east. This space he subdivides into five groups, which, for m y purpose, it is unnecessary to enumerate. M y collections were made in Malabar, Madras, Orissa, and Lower Bengal, up the valley of the Ganges, in the North-West Provinces and the Punjaub, and through Burmah to as far as Mergui in Tenasserim. In this wide extent of country many fishes have doubtless escaped m y observation ; still I have obtained at least a general insight into their distribution. The facts recorded by Hamilton Buchanan, M'Clelland, Sykes, Blyth, and Jerdon are valuable, as either increasing one's knowledge of localities or verifying personal observations ; some references, which I am doubtful about, I am compelled to omit, as when the author is not so accurate in his geography as is desirable for investigations of this description. Siluroids inhabit all fresh waters in India and Burmah-some almost generally, others locally. For an explanation of this I must give a short description of these localities, especially with reference to their ichthyology. These pieces of water consist of rivers, lakes, or tanks, and jheels or swamps. The rivers may be arbitrarily divided into three portions, viz.: - those existing in mountainous districts; secondly, from such to within tidal influence ; and, lastly, the tidal portions. As certain visible results exist due to these three various localities, it will be necessary to explain what their local causes are. The hill-rivers, or rather those which take their rise in hill-ranges, consist of two very distinct classes, namely those which have and those which have not alpine sources. Generally speaking, the rivers which possess alpine sources, as those which descend from the Himalayas, are chiefly replenished by the melting of snow at their origins during the hot months of the year, consequently a diurnal rise and fall in them is apparent, corresponding to the distance from their snowy sources. During the monsoon or rainy season, doubtless the rains also assist in the melting of the snow, exclusive of which, however, they are sufficient to fill the rivers in a spasmodic manner. They thus form torrents, rapidly rising and as rapidly subsiding. During the cold season, unreplenished by rains or melting snows, they dwindle down to a small size. Of the fish inhabiting these places, some of the Siluroids possess suckers or adhesive organs on their heads or chests, as is also perceived in the genera Discognathus and Oreinus amongst the Carps. By means of these suckers they retain their hold against rocks and thus prevent themselves from being washed away. In the rivers destitute of alpine sources, as those of the Neilgherries and the Wynaad in Madras, where snow but rarely falls and never remains for months, we have a different state of affairs. Amongst these must be classed the substreams or affluents of the |
