Proceedings of 

 the United States 

 National Museum 



SMITHSONIAN INSTITUTION . WASHINGTON, D.C. 



Volume 114 1963 Number 3470 



A REVISION OF THE NORTH AMERICAN 



ANNELID WORMS OF THE GENUS CAMBARINCOLA 



(OLIGOCHAETA: BRANCHIOBDELLIDAE) 



By Richard L. Hoffman ^ 



Introduction 



The annelid worms of the oligochaete family Branchiobdellidae are 

 for several reasons of more than casual interest to the zoologist. 

 Owing to their singular mode of life as commensal or subparasitic 

 mhabitants of freshwater crayfish throughout the Northern Hemi- 

 sphere, thej^ have departed in numerous respects from the more 

 t3^ical families of the order, and have developed such a leech-like 

 habitus and appearance that for many years the Branchiobdellidae was 

 thought to be a family in the Hirudinea. The problem remains 

 unanswered: is the similarity of the two groups due to convergence 

 influenced by environmental factors, or do the oligochaetes represent 

 a way station along the evolutionary path taken by leeches? The 

 life history has been worked out for none of the species, nor do we 

 know more than a few inferential details about the distribution of any 

 of them. Branchiobdellids should compel the interest of investigators 



' Department of Biology, Radford College, Radford, Virgina. 



271 



