FISH ENTOZOA FROM YELLOWSTONE PARK. 557 
NOMATODA. 
The nematods infesting the fishes of the National Park do not appear 
to be very numerous either as to species or individuals. Moreover, 
the specimens which were found on the expedition were, with the ex- 
ception of those of one species, encysted or otherwise immature forms. 
Since there is much consequent uncertainty attending their proper 
identification I shall refer to them somewhat cursorily under the head 
of the several hosts. 
SALMO MYKISS. 
A parasite which is found rather frequently in greater or less abun- 
dance, usually in the vicinity of the pyloric cceca of the trout; agrees 
very closely with Dacnitis globosa Dujardin, from Salmo fario. 
The species D. globosa is not recognized by Von Linstow in his *“‘ Gom- 
pendium der Helminthologie,” but is apparently regarded by him as iden- 
tical with Cucullanus globosus Zeder. On account of its close agreement 
with Dujardin’s description of D. globosa, I have used that name in the 
explanation of the figures (P1. 67, Figs. 41 to 46). 
There appear to be two varieties of this worm, or at least of the 
females. In one the body is slender, almost filiform, the female being 
twice as long as the male. In the other the body is not so slender and 
there is not much difference between the sexes with respect to the 
length of the body. - This feature, however, may be accidental. 
This worm may be described as follows: 
Body, white, usually slender, nearly linear, anteriorly narrowing into 
a neck, which expands into a head that is wider than the neck, marked 
with longitudinal strie and with indistinct transverse strie. Head 
subglobose, with two rather thin and corneous lips, the mouth a tri- 
angular slit narrowing dorsally. The head is usually deflected dor- 
sally by a curve in the neck, which resembles a crosier. There is a 
small nodular eminence on the dorsal side of the head. Csophagus 
with thick, strong walls. Female with body usually twice the length 
of the male; reproductive aperture with border raised into prominent 
folds, situated about the posterior third; posterior end acuminate. 
Male usually about half the length of the female, posterior end strongly 
recurved ventrally with a pair of sabre-shaped spicules and a short, 
blunt process behind the pair of spicules and a broad sucker-like 
depression in front of the spicules bearing the anal aperture near its 
anterior end. 
Length of females, 8 to 15 mm.; of males, 7 nm. 
One of the long, slender females was 12 mm. long and 0.2 mm. in diam- 
eter; one of the shorter kind was 8 mm. long and 0.3 mm. in diameter. 
A male, corresponding in appearance with the latter, was 7 mm. long 
and 0.27 min.in diameter. These dimensions are of alcoholic specimens. 
The following additional measurements were made, also on alcoholic 
specimens. The dimensions are given in millimeters: Male, length 
