“5.—ON FISH ENTOZOA FROM YELLOWSTONE NATIONAL PARK. 
" By Epwin Linton, pu. p., 
Professor of Zodlogy in Washington and Jefferson College. 
This paper makes the third which the author has prepared for the 
U. 8S. Fish Commission on entozoa collected in the Yellowstone 
National Park. The first of these papers contained a report on two 
“species of larval cestods, Ligula catostomi from the sucker (Catostomus 
—ardens), and Dibothrium cordiceps from the trout (Salmo mykiss), col- 
lected by Dr. David 8. Jordan in September and October, 1889. The 
Second paper was a special report on the life history of Dibothriwn 
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 Monobothrium terebrans, from its habit of boring a pit 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 J uly, 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. 
i CESTODA. 
Ligula catostomi Lt., Bull. U.S. F. C., 1x, for 1889, pp. 66-72, pl. xx1I-xxv. 
An account of this parasite, based upon specimens found by Dr. 
David 8. Jordan in the sucker (Catostomus 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 
