294 
BULLETIN OF THE UNITED STATES PISH COMMISSION. 
Tlic reproductive aperture is in front of tlio acetabulum. The ovary is subglobular and. lies on 
tlie loft of the median lino and is separated from the acetabulum by the uterus with a few — three or 
four — large ova, and tho shell gland. The latter lies just hack of the acetabulum. On the right side 
of tho median line and at about tho same level as the ovary is the posterior seminal receptacle. Just 
back of tho seminal receptacle and ovary, and lying across the median line, is a lozenge-shaped mass 
of vitelline substance, apparently a yolk reservoir, with ducts leading to the right and left to the 
voluminous vitelline glands. These glands occupy the lateral margins of the body from the posterior 
end to the pharynx. 
Dimensions in millimeters: (1) In sea water, length variable, but from 0.7 to 0.9; breadth 0.4; 
oral sucker, length 0.10, breadth, 0.12; acetabulum, length 0.10, breadth 0.09; ova, longer diameter 
0.11, shorter diameter 0.07. (2) Specimen mounted in balsam, length, 1.3; greatest breadth 0.64; 
diameter of oral sucker 0.17 ; diameter of acetabulum 0.13; length of pharynx 0.28; breadth of same, 
0.25; distance between suckers (margins) 0.14. In one case where the acetabulum was 0.10 long and 
0.11 broad, an ovum measured 0.117 and 0.076 in the two principal diameters. 
Distomum dentatum sp. nov. 
(Plate 3!), figs. G4-G7, XT. S. N. M. No. 0518.] 
A few small distoma from tho flounder ( Paraliclithys deniatus), resembling in many important 
particulars the species which I have called D. tenue (Proc. U. S. Nat. Mus., vol. xx, p. 535, pi. lii, figs. 
2-8), are here included. 
Tho following description is based mainly on specimens mounted in balsam: Body somewhat 
depressed, increasing in breadth toward posterior end, the proportions varying with different stages 
of contraction, but posterior end usually bluntly rounded, greatest diameter usually at the posterior 
testis; neck short, conical, cylindrical in front, somewhat depressed at base; neck and body covered 
with short, sub triangular, scale-like spines, which are densely placed anteriorly, hut become scatter- 
ing at posterior fourth and very sparso at posterior end; ventral sucker sessile, larger than oral 
sucker, nearly circular in outline, with transverse aperture, situated about the anterior third, though 
in some cases whore the neck was contracted tho suckers were closer together and the acetabulum 
was then in advance of tho anterior third ; mouth terminal, surrounded by double circle of straightisli 
spines, about 24 in each circle, the spines of one circle alternating with those of the other; the 
oblong pharynx is separated from the oral sucker by a distance approximating its own length, lies 
close to tho front edge of tho acetabulum, and opens directly into the intestine. 
The branches of the intestine extend to the posterior end of the body. The cirrus pouch, with 
tho inclosed seminal vesicle, lies behind the acetabulum and a little to the right. The cirrus passes 
along the right dorsal edge of the acetabulum, while the distal end of the uterus passes on the dorsal 
left edge of the same, both coming together at the reproductive aperture in front of the acetabulum, 
about on the median lino. Behind the cirrus pouch and in front of the ovary is the uterus, containing 
a comparatively small number (40 estimated iu one) of ova. Tlic ovary lies a little to the right of 
tho median line, immediately in front of the anterior testis, appearing somewhat triangular in outline. 
The testes are two, large, quadrangular in outline, broader than long, median, approximate, the 
junction between them not far from posterior third of the body. The vitellaria are very abundant, 
massed posteriorly, along the lateral margins even into the neck, and around the periphery of the 
body over the other organs. 
Dimensions, in millimeters : 
(1) Living specimen: Length 1.14, anterior diameter 0.14, median breadth 0.37, diameter of oral 
sucker 0.08, diameter of acetabulum 0.14, longer diameter of ovum 0.07, shorter diameter of ovum 0.03. 
(2) Specimen mounted in balsam: Length 1.85, anterior diameter 0.17, greatest breadth 0.64, 
diameter of oral sucker 0.14, diameter of acetabulum 0.20, length of pharynx 0.14, diameter of pharynx 
0.10, length of anterior testis 0.21, length of posterior testis 0.28, breadth of each testis 0.31, longer 
diameter of ovum 0.06, shorter diameter of ovum 0.03, length of longest oral spines 0.04. 
When these specimens are compared with I). tenue, besides being considerably smaller they are 
relatively broader and much more appressed. The number of oral spines is different, although this 
difference should not bo made much of, since observations on a great number of specimens are needed 
to determine what variations, if any, occur in this respect iu these species. 
