FOUR NEW SPECIES OF TREMATODE WORMS FROM 

 THE MUSKRAT, ONDATRA ZIBETHICA, WITH A KEY 

 TO THE TREMATODE PARASITES OF THE MUSKRAT 



By Emmett W. Price 



Parasitologist, Zoological Division, Bureau of Animal Industry 

 United States Departinent of Agriculture 



This paper contains descriptions of four apparently new species of 

 trematodes from the American muskrat, Ondatra zibethica. These 

 parasites belong to four families, representatives of two of which 

 have not been reported previously from this host. For convenience 

 in identifying trematodes which have been reported from the musk- 

 rat, a key to the species is appended. 



Family PSILOSTOMIDAE Odhner, 1913 



PSILOSTOMUM ONDATRAE, new species 



Figure 1 



Specific diagnosis. — Psilostomum: Body ovoid, 1.6 to 2 mm. long 

 by 315/^1 to 961/x, wide in the region of the anterior testis, flattened 

 dorsoventrally. Cuticular spines were not found on specimens from 

 the muskrat, but in view of the fact that the specimens showed some 

 evidence of maceration, it is probable that they had become detached 

 before fixation; specimens of what appear to be the same species 

 from Larus calif ornicus showed spines distributed over the entire 

 body in alternate transverse rows. Oral sucker subterminal, 150;a 

 to 155/i in diameter ; oral aperture slitlike to oval in shape. Acetab- 

 ulum transversely elongated to almost circular in shape, strongly 

 muscular, 220ju, to 300ju, by 300/a to 375/^, situated 525/1, to 537/a from 

 the anterior end of the body. Prepharynx 38ju, to 75/* long, the 

 length depending on the amount of contraction of the anterior part 

 of the body. Pharynx strongly muscular, 112/1 to 127/a long by 82/x, to 

 105/x wide. Esophagus slender, 75/x, to 112//, long; intestinal ceca 

 simple, extending to within a short distance of the posterior end of 

 the body. The excretory system can not be followed with certainty 



No. 2870.— Proceedings U. S. National Museum, Vol. 79, Art. 4. 



52399—31 1 



