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. 



