OBSERVATIONS ON THE INVERTEBRATE FAUNA 

 OF THE KUMAON LAKES. 



III. The Freshwater Moixusca. 



By B. Prashad, D.Sc, Assistant Superintendent, Zoological 

 Survey of India. 



The present paper on the Mollusca of the Kumaon Lakes is a 

 continuation of the two papers published by Dr. N. Annandale 

 and Dr. S. W. Kemp in 1912 ] on the Invertebrate Fauna of the 

 Kumaon Lakes. It is based on a small collection of molluscs made 

 by Dr. Kemp in 1911, and the large series of specimens obtained 

 by Mr. S. L. Hora and myself from the various lakes and streams 

 in August, 1920. The lakes visited were: Naini Tal, Sariya Tal, 

 Khurpa Tal, Sukha Tal, Bhim Tal, Naukuchia Tal, Sat Tal, Damianti 

 Tal and Malwa Tal. Collections were also made in the hill-streams 

 running in the vicinity of these lakes. Notes on the situation, 

 etc., of most of these will be found in the paper cited already, and 

 I only include here a few general observations on the physical 

 conditions of the lakes during August, 1920, with more detailed 

 notes on the areas not visited by Dr. Kemp in 191 1. 



The water-level in all the lakes was much higher at the time 

 of our visit than at that of his, owing to large quantities of water 

 that had been brought during the rains from the extensive catch- 

 ment-areas around each of them ; the area of the lakes also was 

 much larger. The shallower regions of the lakes, which in May, 

 191 1, had been found to harbour rich growths of sponges and 

 Polyzoa, had five to six feet of water, and sponges and Polyzoa 

 were practically non-existent. The water in most of the lakes 

 was clear and held very little mud in suspension. 



All the lakes with the exception of Malwa Tal had, along the 

 margins and up to a depth of about ten feet, thick growths of 

 aquatic plants such as Chara, Potamogeton, Hydrilla and Nelumbium 

 and large quantities of algae, such as Spirogyra. Sponges and 

 Polyzoa were in a few cases found growing on the stems and 

 leaves of these aquatic plants. 



The fauna as a whole was very poor. The Peridiniid, which 

 was found to be very common in 1871 2 and rather scarce in 1911, 

 was only found in very small numbers in Bhim Tal and in still 

 smaller numbers in Naini Tal. Leeches were plentiful under 



1 Rec. hid. Mus. VII, p. 129 (1912). 



* Ann. Mag. Nat. Hist. (4) VII, p. 229 (i8;i). 



