No. 478] 



OHIO NAIDID.E 



In fresh water. Europe, North Ameri- 



The species may be separated by the 

 it is possible that a careful study of P. (V(j 

 P. flagcllum, may show that those respons" 

 have overlooked the existence of the snr 

 leidyi and P. serpentina, it appears evide" 

 distinct on other grounds. 



8otir of dorsal bundle smooth. 

 B'. Last segment not provided with (iiiiror- 

 C. Dorsal set^-e of 3d segment not dccid 

 other segments; length Ties iimi. 



