140 PROCEEDINGS OF THE NATIONAL. MUSEUM vol.87 



are described in this paper. Measurements of D. fodiens are neces- 

 sarily based on the single specimen. 



Genus AMPHIMERUS Barker 



AMPHIMEBUS LINTONI, new species 



Synonym: Haemaiotrephus fodiens Linton, 1928 (encysted form). 



Description. — Opisthorcliiinae. With characters of the genus. 

 Elongate trematodes about 15 mm. in length and 0.8 to 0.9 mm. in 

 greatest width, which occurs in the region of the testes. Posterior end 

 broadly rounded, tapering almost to a point at anterior end; body 

 musculature feebly developed. Acetabulum wealdy developed, 0.05 

 to 0.06 mm. in diameter, situated 1.2 to 1.4 mm. from the anterior end. 

 Oral sucker atrophied, mouth terminal, a buccal tube 0.08 to 0.09 

 mm. in length leading from oral opening to pharynx. Pharynx (fig. 

 15, (7) 0.085 by 0.056 mm.; esophagus narrow, 0.08 to 0.1 mm. long. 

 Intestinal crura irregular and equal, parallel to sides of body and 

 extending to posterior end. Testes in posterior end, slightly lobed, 

 longer than wide, and 0.16 to 0.24 mm. in width by 0.30 to 0.38 mm. 

 in length, placed either one in front of the other or slightly tandem. 

 Vas deferens slightly sinuous, passing anteriorly and opening into the 

 common genital pore at anterior margin of acetabulum ; seminal vesicle 

 absent. Ovary lobed, 0.11 to 0.16 mm. long by 0.32 mm. wide, median, 

 anterior to anterior testis. Seminal receptacle oval, 0.17 by 0.73 mm., 

 located immediately behind ovary. Melilis' gland diffuse, in front of 

 ovary. Uterus densely coiled, filled with eggs, extending from ovary to 

 acetabulum and overlapping intestines, especially in its posterior 

 extent. Vitellaria wealdy developed, consisting of four to six fim- 

 briated groups of follicles on each side; the posteriormost group is 

 opposite the posterior testis, and the anterior group near the posterior 

 boundary of the middle fifth of the body. The vitellaria overlap the 

 intestine. Excretory bladder sinuous, Y-shaped, opening slightly 

 subterminal. Eggs yellowish, 0.024 by 0.013 mm. 



Host. — Gavia immer (pancreas). 



Distribution. — North America (Woods Hole, Mass.). 



Cotypes. — Two complete specimens, U. S. Nat. Mus. Helm. Coll. 

 No. 7916. 



Remarks. — Amphimerus lintoni is more like A. elongatus Gower, 

 1938, from ducks than any other species of the genus. Both of these 

 species differ from all other members of the genus in that the oral 

 sucker is completely atrophied. A. lintoni may be distinguished from 

 A. elongatus by the testes, which are more lobed and relatively smaller 

 in the former than in the latter. The mouth opening is subterminal in 

 A. elongatus and terminal in A. lintoni. The vitellaria are much 

 better developed in A. elongatus than in A. lintoni. 



