18 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 81 



to near posterior margin of ovary. Cirrus pouch pestle shaped, 

 extending caudad of acetabuhim ; cirrus spiny as in Orthosplanchnus. 

 Testes oval, tandem in position, situated in anterior fourth of body. 

 Ovary transversely oval, pretesticular ; seminal receptacle absent; 

 Laurer's canal present. Vitellaria composed of rosette masses of 

 radiating cords of follicles, which extend from vicinity of anterior 

 testis to posterior end of body. Uterus with few coils confined to 

 intercecal space between ovary and acetabulum; vagina well devel- 

 oped, unarmed. Eggs triangular in cross section, slightly thickened 

 at posterior pole. Parasites of cetaceans. 



Type species. — Hadwenius seymouri^ new species. 



HADWENIUS SEYMOURI, new species 



Plate 6, Figures 23-25 



Description. — Hadwenius : Body slender, 27 mm to 60 mm long by 

 1.5 mm to 2 mm wide, and almost circular in cross section. The 

 cuticle of the interior part of the body is spiny, the spines being 

 about 27)a long by 7/x wide and arranged in alternating transverse 

 rows; they are deep-set in the cuticle so that only the tips project 

 above the surface. The rows of spines are close together in the 

 region immediately caudad of the oral sucker, but become farther 

 apart as they approach the region of the anterior testis, where they 

 disappear completely. The oral sucker is cup shaped, 1.8 mm to 

 2 mm long by 1.7 mm to 2 mm in diameter, the thickness of the wall 

 being about 190/i, ; the oral aperture is 540jm to 900|U, in diameter and 

 slightly subterminal. The acetabulum is transversely oval, 930/1, 

 to 1.2 mm long by 1.3 mm to 1.5 mm wide, and the walls are about 

 180^ thick; the distance between the suckers is from 800/x to 1.6 mm, 

 depending upon the degree of contraction. The length of the pre- 

 pharynx is variable; in some specimens it is about 810/x long, while 

 in others the pharynx is drawn into the base of the oral sucker so 

 that the prepharynx is very wide and short. The pharynx is 900ju, 

 to 1 mm long by 620/^ to 900/x wide. The esophagus is very short and 

 wide. The intestine is H shaped as in other members of the sub- 

 family; the ceca are straight and without lateral or median diver- 

 ticula. The excretory pore is situated at the summit of a papillalike 

 prominence, which projects into a deep pit or depression at the 

 posterior end of the body. The excretory vesicle is similar to that in 

 other members of the subfamily. The genital aperture is situated 

 immediately in front of the anterior margin of the acetabulum; 

 it communicates with a spacious genital sinus. The cirrus pouch is 

 pestle shaped, about 1.8 mm long by 560/x wide ; it extends caudad a 

 little more than half the distance between the acetabulum and 



