1920] Allen: Plankton of the San Joaquin River 111 



No eopepods other than the forms already noted were recorded 

 from the 1913 eoUeetions. Since most of the Entomostraca were quite 

 well preserved, it may be possible to make a critical study of the 

 group at a later period. 



MALACOSTRACA 



Three specimens, probably Gammarus sp., were found at Station 

 III in January, 1913. They were taken from very shallow water be- 

 fore the best place for collecting was found and they were evidently 

 adventitious in the plankton. 



MISCELLANEOXJS 

 Glochidia spp. 



station I Station II Station III Daily Hourly 



Average 256 6,415 471 723 



General identification certain. May include larvae of several 

 species of fresh water clams. Recorded three times at Station I in 

 July and August and five times at Station III, mostly in the same 

 period. At Station II the numbers were much larger and the catches 

 more numerous. Recorded three times in January and February in 

 very small numbers and almost continuously in June and July. Sew- 

 age evidently detrimental and flood water favorable to occurrence in 

 the plankton. Effect of temperature uncertain. 



Macrohiotus sp. 



station I station II Station III Daily Hourly 



Average 80 854 2,263 



Identification satisfactory. All the Tardigrada found were referred 

 to this genus. It was only recorded twice at Station I, eleven times 

 at Station II and three times at Station III, always in small numbers. 

 Evidently adventitious. 



Nematoda sp. 



station I Station II Station III Daily Hourly 



Average 212 185 424 



Identification of the order certain. Nothing definite known as 

 to generic classification. Very many specimens were immature. Re- 

 corded six times at Station I in small numbers and at wide intervals, 

 twice at Station II, and five times at Station III, these five being 

 taken in the first three months. These are evidently adventitious 

 forms in the plankton. 



