PLACOBDELLA PEDICULATA n. sp. 1 



ERNEST E. HEMINGWAY 

 University of Minnesota 



In the summer of 1889, while at Lake Pepin super- 

 intending the zoological work of the Geological and 

 Natural History Survey of Minnesota, Professor Nach- 

 trieb found that some of the sheepsheads (Aplodinotus 

 grunniens) which were being seined from the lake in 

 large numbers by the local fishermen had a large parasitic 

 leech fastened to the isthmus or shoulder under the gill 

 cover. Three of these leeches were collected at that time, 

 with portions of the fish showing the place and manner of 

 attachment, One of these specimens was later sent to 

 Professor J. Percy Moore, who found it to be a new 

 species of Placohdella and suggested the specific name 

 pediculata. All the specimens originally collected were 

 adults, gorged with blood, and greatly modified in form 

 from the usual Placohdella types by their close parasitic 

 habit; so that, in some parts, annulation and many other 

 external features had been entirely obliterated. It was 

 seen at once that to determine these features younger and 

 better-preserved specimens must be obtained. Accord- 

 ingly, during the first part of September, 1903, I spent 

 several days with the fishermen around the head of Lake 

 Pepin examining fish for this leech. During this time 

 I examined many hundreds of fish and succeeded in ob- 

 taining three small specimens, none of which were over 

 a centimeter in length. 



Habits 



Placohdella pediculata appears to be a true fish para- 

 site, having been found only in the gill chamber of the 



1 From the laboratory of the Department of Animal Biology, the Uni- 

 527 



