3 -ON TWO SPECIES OF LARVAE DIBOTHRIA FROM THE YELLOWSTONE 
NATIONAL PARK. 
BY EDWIN LINTON. 
[Plates XXIII to XXVII.] 
In December, 1889, I received an interesting lot of entozoa, collected in the Yel- 
lowstone National Park by Dr. David S. Jordan of Bloomington, Iiid., cliieliy during 
October, 1889. The collection submitted to me for examination consists of two trout 
( Salmo mylciss), with the viscera of three others, four suckers ( Catostonms ardens J. & G . ), 
and a few large Ligulce that had been removed from the abdominal cavity of the latter 
host. The trout were obtained in the Yellowstone River just below the lake, while the 
suckers were from Witch Greek, a hot tributary of Heart Lake. 
Dr. Jordan states that the parasites of the trout first appeared, so far as he ob- 
served, in cysts among the pyloric coeca, later in the liver and among the viscera, and 
finally reaching a length of 5 inches in the flesh of the abdomen. These parasites were 
found in all trout in lakes fed in part by geyser-water, the trout abounding in the 
warm water in consequence of the abundance of food there. 
Ot the suckers he states that they abound in the warm waters, ascending to the 
temperature of 80° or more. About one in four has a very large parasitic worm in tlie 
abdominal cavity, where it is often as large as the whole viscera, and lies along the 
middle line of the belly. These worms were often more than a foot long and inch 
broad. 
REMARKS ON THE GENUS LIGULA. 
The generic name Ligula has long been used for certain cestods of the family Dihotli- 
riidm {PseudophyUidcB Van Beneden). The genus was distinguished from the genus 
Dibothrium {Bothriocephalus) chiefly by the absence of distinct segments in tlie bod^L 
The forms referred to this genus are common inmany of the fresh- water fishes and are 
especially abundant in the Percidw and Cyprinidee, where tliey occur in the abdominal 
cavity and body-wall of their host. The adult stage has not been found in fishes. 
The admirable researches of Duchamp (1876) first proved the identity of the Lig- 
ulse of fishes with forms which are adult in the intestines of dilfereut aquatic birds. 
Duchamp’s investigations were on an abdominal Ligula of the tench [Tinea vulgaris). 
This Ligula has a most extensive synonymy, but the name which has priority is L. 
siwipbrnsima Kudolphi. Diesiug (1864) recognizes two species of Ligula, viz, L.mon- 
ogramma Orepliu (a synonym of L. simplicissinia) and L. digramma Greplin. 
It is proposed by Donnadieu (1877) to unite all the species of Ligulie in one and 
the same species, in the genus Dibothrium with the specific name Dibothrium ligula. 
65 
Bull. U. S. F. C. 89 5 
