46 PROCEEDII^rGS OF THE NATIONAL MUSEUM vol.88 



imately to the middle of the postacetabular region; genital aperture 

 on right side of neck, near margin, about on a level with the fork- 

 ing of the intestine; cirrus pouch in front of ventral sucker, oval- 

 elliptical with thick walls, containing prostatic cells; seminal vesicle 

 in two divisions, inclosed in cirrus pouch; testes opposite, at level of 

 ventral sucker. The position of the testes is somewhat variable. In 

 some cases they extend in front of the ventral sucker ; in others they 

 lie at the level of the posterior border of the ventral sucker, even 

 extending for a short distance back of it. The ovary lies behind the 

 ventral sucker, on or near the median line, either to the right or to 

 the left of it ; shell gland at posterior border of ovary ; seminal vesicle 

 and vitelline gland behind the ovary, their relative positions some- 

 what variable. Thus, in one the ovary was at the posterior edge of 

 the ventral sucker, the seminal receptacle on the median line, with 

 the vitelline gland on the left side. In another the seminal receptacle 

 lay behind the vitelline gland. The folds of the uterus occupy the 

 greater part of the postacetabular region. The ova, which in the 

 older portion of the uterus may contain ciliated miracidia, are about 

 0.07 by 0.03 mm. in size in balsam. The metraterm passes on the 

 right side of the ventral sucker to the genital pore. There is a large 

 excretory vessel at the posterior end, the excretory pore being sur- 

 rounded by rosettelike musculature. 



As a rule these distomes do not much exceed 1 mm. in length. 

 Measurements, life, flattened under cover-glass: Length, 0.8 mm.; 

 breadth, anterior, 0.15 mm., at level of ventral sucker, maximum, 

 0.42 mm., at posterior end 0.1 mm.; oral sucker, length, 0.14 mm., 

 breadth, 0.11 mm.; pharynx, length, 0.03 mm., breadth, 0.05 mm.; 

 ventral sucker, length, 0.21 mm., breadth, 0.23 mm.; ova 0.068 by 

 0.028 mm.; an ovum containing a ciliated embryo measured 0.072 

 by 0.028 mm. 



Type specimens. — U.S.N.M. No. 8193 (holotype and paratypes). 



Hosts. — Tautog {Tautoga onitis), round herring {Etrumens- 

 sadina) . 



Record of collections. — Twenty -six (U.S.N.M. No. 8193), collected 

 July 27, 1904, from one tautog; small, fusiform, reddish yellow; 

 ventral sucker showing a tinge of red. At first the worms were 

 contracted and somewhat concave ventrally. When flattened the 

 outline is almost rhomboidal. Two, lying free in sea water, measured 

 0.41 by 0.23 mm. and 0.38 by 0.26 mm., respectively. When flattened 

 the length increased to 0.8 mm. 



Eighteen, collected August 9, 1904, from one tautog. One of 

 these, rather larger than the others, was noted in which ova had not 

 yet appeared. The uterus, in many folds, filled the posterior end of 

 the body. 



