554 RKPORT OF COMMISSIONER OF FIftll ANH F'SHERIFS. 



<i'soj)liagns. Intestinal ciura continued almost to the posterior end. 

 Vitelline glands numerous, not only occiipN in u the margins of the body 

 as far as the middle of the necic, hut also all the region behind the 

 testes. Trans\erse duet with vitelline receptacle in front of the testes. 

 Testes two, subgiobose, median, approximate with each other. Ovaiy 

 globular, one-hnlf the size of a testis, remote. Gyri of uterus few, 

 situated in front of the testes, (xenital apertures api)osed in middle 

 of neck. Bursa of i)enis long, smooth, cylindrical. Excretory vessel 

 a median ca*cum, desisting in front of testes and oix'uing in a i>osterior 

 caudal pore. Length (I mm., breadth 1.5 nun. 



This description is adapted, with a few changes, from Olsson, cited 

 above. 



Habitat: Sahtw mylciss, lectum. Heart Lake and Yellowstone Lake, 

 July and August. 



A distomiim which 1 have found frequently in the Rocky Mountain 

 trout appears to be identical with 7>. laureatum, a parasite which infests 

 several European fishes, e. //., Thymailvs indgariSy Coregonus oxyrhyn- 

 chus, and Balmo fario. 



The dimensions given by Dujardin for this species are: Length, 12 to 

 3.35 mm.; breadth, 1 to 1.22 mm. 



My specimens, alcoholic, measure from 1.5 to 4 mm. in length and 

 0.5 to 1.5 mm. iu breadth. The length is in most cases three 

 or four times the breadth. The diameter of the ventral sucker is 

 about twice that of the oral sucker. The transverse diameter of the 

 aperture of the ventral sucker is three times its axial diameter. The 

 eggs are yellow, elliptical, usually collapsed in alcoIu)lic specimens from 

 0.07 to 0.085 mm. in length and 0.01 to 0.045 mm. in breadth. 



In life the color is yellowish-white; Avith transmitted light the eggs, 

 which are large and not numerous, appear golden -brown. In the 

 living specimens there ap]>eared to be alxmt five low, blunt papilhe on 

 the dorsal half of the circumference of the oral sucker. Subsequent 

 study levealed the nund)er and disposition given above and in the 

 sketches. This parasite' was noticed on several occasions, but usually 

 there were but few — a dozen or two — ^^in each host. 



Detailed measurements of tlu* specimen ligured in h'ig. 2() are as fol- 

 lows: 



Milliiiie.ters. 



Length 3. HO 



(Jrciitest bieadtli 1.00 



Diami'ter of !iiil,»!rior sucker, interior, lateral 0.17 



Diameter of anterior sucker, interior, axial 0. lo 



Diameter of anterior Hueker, exterior 0.'X^ 



Diameter of ventral sucker, interior 0. 1^0 



Diameter of ventral sucker, exterior 0. 13 



