538 Records of the Indian Museum. [Vol. XXII, It is not in my power to give an account of the water-birds of the Loktak Lake, on and around which both swimming and wading birds are extraordinarily abundant. On this subject Hume's X)aper in Stray Feathers, Vol. XI, should be consulted. I have not seen any other place in India where such enormous swarms of ducks and geese could be observed on the water as was the case in February on this lake, and wading birds were almost as abundant in the surrounding swamps. vSome of the latter, notably the smaller Herons, the Open-bill (Anastoinus oscitans) and the Glossy Ibis {Plagadis falcinellus), were proved by examination of their stomach-contents to be feeding mainly on aquatic molluscs, and even the ducks and geese must destroy enormous quantities of molluscan spawn and young with the weeds on which thej' depend maiiily for their food-supply. Otters are said to be abundant, but no specimens were obtained. The fauna of the Loktak Lake must, therefore, be regarded as paludine rather than lacustrine. It is comparable to that of the marginal zone of the Inle Lake rather than to that of the central region. Even from the former, however, it differs notably. The great abundance of different species of small bottom -haunting fish, the greater poverty of the arthropod fauna and the absence of several molluscan genera (Pachylabra,' all the Hydrobiidae, Seg-mentina, etc.) usually found in such situations are noteworthy features, and may be correlated directl}^ with the superabundance of vegetation and indirectly with the composition of the water and therefore, still more indirectly, with the geological formation of the surrounding country and the meteorology of the valley. The absence of extreme specialization in the aquatic fauna may be put down partly to the same causes and partly to the absence of complete geographical isolation, while the curious fact, amply illustrated in the following paper, that, though the Imphal River belongs to the Irrawadi system and is cut off by high ranges of mountains from those of Assam, nevertheless the aquatic molluscs are essentially Assamese and include very few Burmese species — this fact would at any rate suggest that compre-hensive physiographical changes have taken place in the Manipur valley and the surrounding hills at a date geologically not remote. THE PROSOBRANCHIA. Bv N. Annandale. This order is represented in the aquatic and amphibious fauna of Manipur by eleven species, belonging to the famiHes Hydrobiidae, Viviparidae, Melaniidac and AmpuUariidae. With one exception, that of the Viviparid genus Lecythoconcha , the genera are those usually found in the tropical districts of India, and this section of ' The place of this genus is taken to a large extent by sjigantic Viviparidae.
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