VII.— DIATOMS (PLEURASIGMA) (X 130 dia.). 

 This represents a typical form of oyster food. At times this form of 

 diatom is so abundant that it constitutes 85 per cent of the planlston towings, 

 and often as much as 96 per cent of the stomach contents of the oyster. This, 

 however, represens only one type of oyster food. 



