5.-0N FISH ENTOZOA FROM YELLOWSTONE NATIONAL PARK. 



By Edwin Linton, i-h. d., 

 Professor of Zoologtj in Washington and Jefferson College. 



This paper makes the third which the author has prepared for the 

 U. S. Fish Commission on entozoa collected iu the Yellowstone 

 National Park. The first of these x^apers contained a report on two 

 species of larval cestods, Ligula catostomi from the sucker {Catostonms 

 ardens), and IHhothrmm cordiceps from the trout {Salmo myJciss), col- 

 lected by Dr. David S. Jordan in September and October, 1889. The 

 second paper was a special report on the life history of Bibothrmm 

 cordiceps, being the result of the author's investigations, in July and 

 August, 1890, into the cause of the excessive parasitism among the 

 trout of Yellowstone Lake. The present paper contains descriptions 

 of other fish entozoa which were obtained incidental to the inquiry 

 into the life history of D. cordiceps. 



Aside from the trout parasite (D. cordiceps), perhaps the most 

 interesting form encountered was^the monobothrium from the sucker; 

 this appears to be an undescribed species, and I have given it the 

 name Monobotlirium terehrans, from its habit of boring a j)it in the 

 mucous membrane of its host. I have thought it best also to give a 

 brief account of the anatomy of this singular worm. Some additional 

 notes on the ligula of the sucker have been given. These are based 

 on observations made in July, 1890. That part of the report which 

 relates to the nematods is necessarily imperfect, owing to the fact that, 

 with the exception of the species Dacnitis globosa from the trout, the 

 specimens were all immature and for the most part few in number. 



CESTODA. 



Ligula catos*omi Lt., Bull. U. S. F. C, ix, for 1889, pp. 66-72, i)l. xxiii-xxv. 



An account of this parasite, based upon specimens found by Dr. 

 David S. Jordan in the sucker {Catostonms ardens), of Witch Creek, a 

 tributary of Heart Lake, Wyoming, was published in the Bulletin of the 

 United States Fish Commission, cited above. It is not proposed to give 

 any further account of the anatomy of this species here, but simply to 

 record a few notes and observations. 



On July 28, 1890, I found in a young sucker, captured in a small 

 warm stream near our camp on Heart Lake, a ligula, in the abdominal 

 H. Mis. 113 35 545 



