Bulletin of the Museum of Comparative Zoology 

 AT HARVARD COLLEGE. 



Vol. XXXVI. No. 2. 



SOME NORTH AMERICAN FRESH-WATER RHYNCHO- 

 BDELLID^, AXD THEIR PARASITES. 



By W. E. Castle. 



With Eight Plates. 



CAMBRIDGE, jMASS., U. S. A. : 



PRINTED FOR THE MUSEUM. 



August, 1900. 



