FISH ENTOZOA FROM YELLOWSTONE TARK. 557 



NUMATODA. 



The ueinatods infesting the fishes of the National Park do not appear 

 to be very nnmerous eithei: as to species or individuals. Moreov^er, 

 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 coeca of the trout; agrees 

 very closely with J)acnitis (jJobosa Dujardin, from Salmo fario. 



Tlie species D. glohosa is not recognized by Von Linstow in his " Coni- 

 IK'ndium dcr Helmintholofjie,'''' but is apiiarently regarded by him as iden- 

 tical with Cucullanus glohoaus Zeder. On account of its close agreement 

 with Dujardin's description of I), (/lohosa, I have used that name in the 

 explanation of the figures (PI. 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 dififereuce 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 strife and with indistinct transverse strite. Head 

 subglobose, Avith 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. QEsophagus 

 with thick, strong walls. Female with body usually twice the length 

 of the male; reproductive ai^erture 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 si)icules bearing the anal aperture near its 

 anterior end. 



Length of females, 8 to ]5 mm.; of males, 7 mm. 



One of the long, slender females was 1.5 mm. long and O.U 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.-i7 mm. 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 



