290 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



anterior sucker 1, breadth through acetabulum 1.25, breadth at posterior fourth 1 4, distance between 

 suckers 1.1, thickness behind acetabulum 1.1, thickness at acetabulum 1.5; (2) from sections, trausver.se 

 diameter of oral sucker 0.68, vertical diameter of same 0.47, transverse diameter of pharynx 0.34, 

 vertical diameter of same 0.28, length of same (estimated) 0.28, transverse diameter of acetabulum 

 1.03, vertical diameter of same O.G5, greater diameter of ova 0.034 to 0.041, lesser diameter of ova 0.017, 

 transverse diameter of ovary 0.48, vertical diameter of same 0.24, length of same (estimated) 0.30. 

 Some of the details of structure are shown in the sketches, ligs. 29-37. 



Distomum vitellosum sp. iiov. 

 [Plate 37, figs. 38, 39, U.S.N.M. No. 0513.] 



Three small distoma associated with others referred to D. ocreatum Moliu, in the hake (Mcrlucciiis 

 Irilinvai'is), collected August 29, are here described. They were distinguished from the others at the 

 time of collecting by their slender conical necks, very prominent acetabulum, relatively large ova, 

 and having the posterior part of the body tilled with subaugular vitelliue masses. 



The species is probably new. It would seem to be a member of a group of species of which 

 I), nmbriniv Stossich, D. oboratitm Molin, and D. mormyri Stossich are representatives. The characters, 

 so far as they can be made out from my specimens, are: Body smooth, subcylindrical; neck short, 

 slender, conical, very contractile in life, in preserved specimens arched above, concave and hollowed 

 out beneath; mouth subterminal, aperture transverse; pharynx, immediately following oral sucker, 

 elongated; (.esophagus not made out, but either none or very short; branches of intestine simple, not 

 spacious, extending to near the posterior end; acetabulum much larger than oral sucker, prominent, 

 aperture contracts to small, transverse opening with puckered margins, situated about anterior third 

 in preserved specimens. Aperture of reproductive organs in front of acetabulum, on left of median 

 line; testes two, moderately large, median, approximate, and situated near posterior end; ovary in 

 front of anterior testis and touching it, lying on median hue, but a little toward the right; vitellaria 

 consisting of numerous rather large subangular masses, which till the body behind the testes and 

 extend along the sides as far forward as the acetabulum; ova not numerous and rather large, lying 

 between ovary and acetabulum. 



Dimensions in millimeters: (1) Of a specimen in glycerin, length 1.42, diameter of oral sucker 

 0.08, diameter of acetabulum 0.25, longer diameter of ova 0.052, shorter diameter of ova 0.031; (2) of 

 a specimen in balsam, length 0.88, diameter of anterior sucker 0.10, diameter of acetabulum 0.17, 

 greatest breadth of body 0.25, length of neck 0.22, longer diameter of ova 0.058, shorter diameter of 



ova 0.034. 



Distomum pudeiis sp. iiov. 



[I'late 37, ligs. 40-47, U. S. N. M. No. 0514.] 



Certain distoma from the common llounder (Pardliclithys dcnl(itun) collected September 5 were 

 thought at lirst to be identical with JUtstumiim sp. from the same host, described on page 29l>; but when 

 examined more closely were found to be different. The alimentary canals of four flounders were 

 washed out and, after repeated washing and decanting, a large number of distoma were obtained. 

 These are of various shapes and sizes, but appear to belong to the same species. The largest when 

 living measured from 2.7 to 3.7 mm. in length, with maximum breadth of about 0.8 mm. One of the 

 smaller specimens measured 1.2 mm. in length and 0.42 mm. in breadth. 



The following description is based on preserved material: Body smooth, ovate to linear obJong, 

 somewhat depressed; neck variable, conical, tapering to mouth, or often shortened by inversion of 

 anterior end; mouth terminal, unarmed; oral sucker nearly circular in outline in a few cases, but in 

 most considerably broader than long; acetabulum nearly circular in outline, i. e., when viewed either 

 from the dorsal or ventral side, and considerably larger than the oral sucker, situated not far from 

 the anterior fourth; pharynx pyriform, with the posterior end the larger, proportions not uniform. In 

 some cases the length is greater than the breadth, in some it equals the breadth, and in some it is less 

 than the breadth ; separated from the oral sucker by a distance equal to a little more than its own 

 length and from the intestinal raiui by a distance less than half its length. These proportions are 

 for a specimen in which the neck is extended. When the anterior end is inverted, or even slightly 

 contracted, the pharynx may follow 'the oral sucker very closely. and appear to open directly into the 

 intestinal rami. The walls of the intestine are very thin; the intestinal rami are simple and extend 

 to the posterior end of the body. The excretory vessel was seen to be spacious and thin-walled at the 

 posterior end, but was not seen in anterior part of the body. It should be noted that the specimens 

 had lain overnight in water before they were placed in killing and hardening lluid. 



