JAN 16 1900 



BULLETIN 



OF THE 



S^""^^ L 



LLINOIS XTATE I ABORATORY 



OF 



NATURAL HISTORY 



Urbana, Illinois. 



VOLUME V. 



ARTICLE IX. PLANKTON STUDIES. III. ON PLATY- 

 DORINA, A NEW GENUS OF THE FAMILY VOLVOC- 

 IDA<:, FROM THE PLANKTON OF THE ILLINOIS RIVER. 



By C. a. KOFOID, Ph. D. 



Illinois State Laboratory of Natural History, 



URBANA, ILLINOIS. 



December 28, J 899. 



