12 THE HANCOCK PACIFIC EXPEDITIONS VOL. 2 



is approximately equally wide, except at the anterior and posterior 

 fourth. The acetabulum is well anterior to midbody, the forebody 

 being usually 1/4 to 1/5 total body length. Both suckers are sub- 

 circular with a tendency to be slightly longer than wide. The oral 

 sucker is 0.225 to 0.315 mm. in diameter. The acetabulum is 0.352 

 to 0.502 mm. in diameter. Its aperture is transverse. The sucker ratio 

 is approximately 2:3 or 3:5. Young specimens show a few pigment 

 granules dorsally in the forebody but these are lacking in older 

 specimens. 



There is a short but distinct prepharynx. The pharynx is longer 

 than wide, 0.142 to 0.202 by 0.112 to 0.165 mm. Its anterior fourth 

 is modified as a sphincter region composed of circular muscles (sug- 

 gesting the character of the pharynx in Gyliauchen) while the pos- 

 terior region is composed of radial muscles. There is a distinct 

 esophagus somewhat shorter than the pharynx. The intestinal bifur- 

 cation is approximately midway between the suckers. The ceca are 

 narrow and extend to a point a short distance from the posterior 

 end where the body begins its rather abrupt tapering to the posterior 

 tip. Each cecum ends blindly. 



The excretory vesicle is a long narrow tube extending anteriorly 

 from the pore at the posterior tip of the body to the posterior testis 

 where it spreads slightly to right and left and narrows to become 

 a collecting tube on each side. Each collecting tube shortly after it 

 leaves the vesicle forks into two tubules both extending forward, 

 both at first median to the cecum, the larger tubule median to the 

 smaller. Anterior to the acetabulum they are both lateral to the 

 cecum. They seem to end near the level of the pharynx. Posterior 

 to the level of the testes a very small excretory tubule can be seen 

 on each side. These two posteriorly directed tubules arise at the 

 same point where the anterior tubules unite. They extend to the 

 posterior end of the body. 



The lymphatic system consists of four longitudinal vessels 

 close to the intestinal ceca, sometimes median, sometimes dorsal and 

 ventral. Two of these lymphatic vessels extend anterior to the oral 

 sucker to the extreme anterior end of the body where they end 

 blindly. The longitudinal vessels do not give off" side branches ex- 

 cept in the posterior half of the body. Shortly behind the testes 

 vesicle-like portions of the lymphatic system appear in the extreme 

 lateral regions of the body. These are especially numerous near the 



