ROTATORIA 1/7 



confined to this zone. The 9 locahties lying alcove 4500 m. may best be considered in three 

 groups. 



4500-4600 (3 locahties) 



Brachionus plicatilis 



B. capsuliflorus f. ensii 

 Ceplialodclla gibba 



C. wiszniewskii 

 Ifiira aurita 

 Kcratella quadrata 

 Lophocaris oxysternon 

 Notholca striata 

 Notonitnata epaxia 

 Polyarthra trigla 

 Pompholyx sulcata 



4600-5000 m. (3 localities) 

 Eosphora najas 

 Euchlanis mcneta 

 E. parva 



Kcratella quadrata 

 K. cochlcaris 

 Lepadella patella 

 Mytilina trigona 

 Notholca striata 

 Polyarthra trigla 

 Squatinella niutica 



5000-5334 m. (3 localities) 

 Filinia longiseta 

 Kcratella cochlcaris 

 Pcdalia bidgarica 



It would seem that the increasing rigor of the environment with increasing altitude 

 plays a considerable part in reducing the rotatorian fauna but that in the region studied the 

 limiting factors do not become very intense until an altitude of about 5000 m. is attained. 

 The localities above that altitude may therefore be profitably examined more closely. 



Togarma Tso, altitude 5217 m. (Figure 6). 



Three small ponds lie close together in the wide valley that ends to the North in the 

 pass called Ororotse La, above the Ororotse Tso. The smallest pond is about 30 m. long, 

 15 ni. wide and 30 cms. deep. Both the largest and smallest ponds yielded Pcdalia bidgarica, 

 but no other rotifers were obtained. The water at 11.00 a. m., 10 July, 1932, had a temper- 

 ature of 16.2°C. but during the night probably fell to about freezing point. The chloride con- 

 tent was less than 0.0005 N., the alkali reserve (methyl orange titration) 0.0012 N. and the 

 pH 8.9. In the largest of these ponds an abundant copepod and cladoceran fauna occurred, 

 and much Spirogyra, forming brick-red masses, but no other rotifers were obtained in 

 tow-nettings. The poverty of the rotatorian fauna is emphasized by the fact that these 

 ponds superficially resemble the ponds at Chushol from which a considerable number of 

 species are recorded. 



Ororotse Tso, altitude 5297 m. 



