52 University of California Publications in Zoology [Vol.22 



rather small. Loss through net considerable. Maximum in May at 

 Station II with a well defined pulse. Maximum in August at Station 

 III where there were no definite pulses. May be adventitious. Tem- 

 peratures at maxima were above 20° C. 



Cymbella affinis Kiitz. 



Station I Station II Station III Daily Hourly 



Average 1,283 73,671 10,276 516 20,345 



Identification uncertain. This was a very small Cymbella rela- 

 tively few of which could have been retained by the net. Recorded only 

 eleven times at Station I. Abundant in March, April, May and June 

 at Station II but missing in January, February and December. Scat- 

 tering in other months. Maximum on May 31 in a well developed 

 pulse. More irregular in occurrence at Station III where the maxi- 

 mum came in April. Probably an important planktont numerically. 

 Evidently not favored by sewage. 



Cymbella cymbiformis Kiitz. 



Station I Station II Station III Daily Hourly 



Average 446 8,382 4,331 310 4,561 



Identification uncertain. Probably includes more than one species 

 not distinguishable while counting. Recorded thirteen times at wide 

 intervals at Station I, in small numbers. Small numbers recorded in 

 every month of the year at Stations I and III with a fairly constant 

 record through May and June at Station II. Apparently of minor 

 importance. 



Cymbella tumicla Breb. 



Station I Station II Station III Daily Hourly 



Average 2,245 23,677 3,547 619 5,546 



Identification uncertain. Probably includes more than one species. 

 Records scattering and in small numbers at Station I. Small numbers 

 but fairly constant, May to September, at Station III. Recorded in 

 every month except January and September at Station II. Maximum 

 in May. Probably of minor importance. 



Epithcmia ocellata Kiitz. 



Station I Station II Station III Daily Hourly 



Average 1,015 15,713 3,579 413 8,630 



Identification fairly satisfactory. Probably two other species in- 

 eluded. Loss through net heavy. Numbers small and records scatter- 

 ing at Stations I and III. Representation fairly constant at Station 

 II except in January, February and December. Maximum in May on 

 a well marked pulse. May be adventitious since the maximum comes 

 on the waters of the mountain flood. 



