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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 79 



the cirrus pouch. Testes oval, situated in the median line in the 

 posterior third of the body, and tandem in position; the anterior 

 testis is 172)Li long by 142/x wide and the posterior IST/u, long by 97/i 

 wide, the two testes being separated by a space 120/m wide. The cir- 

 rus pouch is 202^ long by 75/x wide at its base, slightly curved, and 

 situated at the posterior end of the body. The genital pore is sub- 

 terminal, opening on the ventral surface. The ovary is slightly 

 ovoid in shape, 150|U, long by 120/* wide, and situated about 90/* 

 caudad of the acetabulum. The shell gland is poorly defined, situ- 

 ated caudad and slightly to the left of the ovary. The uterus is 

 long, running caudally from the shell gland in irregular transverse 

 loops, passing to the right around the anterior testis and to the left 

 around the posterior testis, and terminating in a short metraterm 

 which opens at the genital pore. The vitellaria are situated lat- 

 erally and composed of small follicles extending from a short distance 



//7?/7? 



Figure 3. — Ueotrema shillingeri. Ventral view 



caudad of the ovary to about the level of the anterior margin of the 

 acetabulum. Eggs oval, 22/a long by 15/x wide, brown in color. 



Host. — Ondatra zihethica. 



Location. — Small intestine. 



Distribution. — United States (Maryland). 



Type specimen.~\J.^.^M. Helm Coil. No. 29725. 



The above description is based upon a single mature specimen 

 collected by Dr. G. Dikmans from the small intestine of a muskrat, 

 the animal having been trapped near Cambridge, Md., and the 

 viscera sent to the Zoological Division by Dr. J. E. Shiiiinger, of 

 the Bureau of Biological Survey. The specimen was dead when 

 collected and showed some evidence of maceration, consequently cer- 

 tain details, such as the presence or absence of cuticular spines and 

 the course of the excretory system, could not be determined. 



This species differs from Urotrema scahriduTn Braun, the only 

 other species of the genus, in body size, relative size of the suckers, 

 distribution of the vitellaria, distance between testes, and the size 

 of the eggs. U. shillingeri is much smaller than U. scahridum and 

 the oral sucker is distinctly smaller than the acetabulum in the 

 former, while in the latter species the suckers are about equal in 

 size; the testes are approximated in U. scahridurn, while in U. skill- 



