6 PROCEEDINGS OF THE NATIONAL MUSEUM VOL.73 



Dimensions, life, uncompressed : Length 1.68 mm. ; breadth, 

 anterior 0.21, middle 0.65; diameter of oral sucker 0.28, of pharynx 

 0.19(?), ventral sucker 0.42; ova 0.088 by 0.064. Length after com- 

 pression 1.96. 



Dimensions in balsam: Length 1.54; maximum breadth 0.70; di- 

 ameter of oral sucker 0.21, pharynx 0.13, ventral sucker 0.33; ova 

 0.08 by 0.05. 



Body more or less fusiform, bluntly rounded at extremities ; ventral 

 sucker much larger than oral, and placed at about the anterior third. 

 It is provided with a sphincter, but does not appear to be as muscular 

 as the oral sucker. Pharynx adjacent to oral sucker; esophagus 

 none; rami of intestine extend to posterior end of the body. The 

 cirrus-pouch is relatively large, thin-walled, long-pyriform, its 

 posterior portion acting as a seminal vesicle. It is dorsal to the 

 A'entral sucker and extends for a short distance in front of the anterior 

 border of the ventral sucker. The genital pore is about on the me- 

 dian line near the posterior border of the oral sucker. The testes are 

 broader than long (length 0.13, breadth 0.27), contiguous, one follow- 

 ing the other on the median line, about half way between the ventral 

 sucker and the posterior end ; ovary oval-elliptical in outline, a little 

 to the left of the median line in front of the testes and near the 

 ventral sucker, length 0.15, breadth 0.13. The vitellaria fill all the 

 space back of the testes and extend in a broad band, approximately 

 equal to one-third the breadth of the body, along each lateral margin 

 to the level of the pharynx. The uterus lies between the first testis 

 and the ventral sucker. It passes along the dorsal side of the ventral 

 sucker a little to the right of the median line, and parallel with the 

 seminal vesicle, to the genital pore. The ova are large, and, consider- 

 ing their size, rather many — approximately 75. 



The most conspicuous feature in the mounted specimen is the widely 

 diffused, brownish red vitelline gland. In life the most stiiking 

 characteristic was the differential coloration. 



Type.~Q2it No. 7919, U.S.N.M. 



PETASIGER NITroUS. new species 



Figures 10-16 



From intestine of horned grebe {Colymbus mi/ritus). 



Small, fusiform; head reniform with 19 spines in a single circle 

 uninterrupted dorsally; length of spines at ventral angles of head 

 0.14, elsewhere 0.12; neck concave ventrally, densely covered with 

 .small spines becoming sparingly scattered on the body; ventral 

 .sucker near the middle of the length, much larger than the oral 

 sucker; pharynx longer than broad, separated from the oral sucker 

 hy a short prepharynx; esophagus long; rami of the intestine begin 



