PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 79 



owing to the maturity of the specimens, but so far as can be ascer- 

 tained from the examination of serial sections, it appears to corre- 

 spond closely to that given by Odhner (1913) in his diagnosis of 

 the genus; excretory pore terminal. Testes large, elongated trans- 

 versely, postequatorial, and tandem in position. The anterior testis 

 is 262/1 to 375)u, long by 412/a to 712/x wide and the posterior testis 

 262/i to 275fi long by 337ju, to 750/x wide. Cirrus pouch piriform, its 

 posterior end never extending beyond the center of the acetabulum ; 

 it contains a voluminous seminal vesicle and a long, slender, unarmed 

 cirrus. The genital pore is situated in the median line about mid- 

 way between the bifurcation of the intestine and the anterior margin 

 of the acetabulum. Ovary ovoid, 75/x by 150fi, situated a short dis- 

 tance in front of the anterior testis and to the left of the median line. 



FiGDEB 1. PSILOSTOMUM ONDATRAE. 



//77/77 

 Ventbal view of specimen from muskrat 



Shell gland well developed, dorsad of ovary. Laurer's canal pres- 

 ent. Receptaculum seminis apparently absent. The vitellaria are 

 composed of large follicles situated laterally and forming a wreath- 

 like mass extending from the level of the pharnyx to the posterior 

 end of the body. Uterus relatively short, consisting of irregular 

 coils occupying the intercecal space between the anterior margin of 

 the anterior testis and the acetabulum, and terminating in a moder- 

 ately developed metraterm. The metraterm extends along the left 

 side of the cirrus pouch and opens into the genital sinus immediately 

 anterior to the male aperture. Eggs oval, 82)u, to 90/x long by 45/a to 

 48/i wide, yellowish brown in color. 



Hosts. — Ondatra zibethica and Larus calif omicus. 



Location. — Liver of muskrat (according to label) ; proventriculus 

 of gull. 



Distribution. — Kirkfield, Ontario, and Klamath Falls, Oreg. 



Type specimens. — U.S.N.M. Helm. Coll. No. 29749; paratypes 

 No. 29750. 



