366 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



level. Eggs thin shelled, 48 to 61 by 26 to 34 /x, averaging 53 by 27 [x. 

 Excretory vesicle extending dorsal to testes to level of ovary. Type host : 

 Paranthias furcifer. 



Comparisons. This species differs from O. inimici Yamaguti, 1934 in 

 its rudimentary lateral acetabular papillae, its more anterior genital pore, 

 smaller eggs, wider testes, arrangement of posttesticular vitellaria, and 

 sucker ratio. O. gonustii Yamaguti, 1938 also has 5 pairs of papillae but 

 differs in many respects such as location of genital pore, shape of testes, 

 extent of vitellaria, and seminal vesicle. 



Opecoelus xenistii, new species 

 (Plates 36 and 37, figs. 38, 39) 



Host: Xenistius calif orniensis (Steindachner) 

 Location: Intestine 



Locality: Tagus Cove, Albemarle Island, Galapagos 

 Number: 7 



SPECIFIC DIAGNOSIS OF OPECOELUS XENISTII 



Size 1.552 to 2.356 by 0.675 to 0.780. Widest posterior to midbody; 

 posterior end broadly rounded. Forebody 1/5 to 1^ body length. Oral 

 sucker 0.157 to 0.193 in transverse diameter; acetabulum 0.292 to 0.330 

 in diameter or slightly less than twice size of oral sucker; acetabulum 

 with transverse aperture and 5 pairs of papillae. The 3 median papillae 

 more prominent, lateral papillae veiy inconspicuous (fig. 39). Short pre- 

 pharynx; phaiynx 0.076 to 0.100 by 0.076 to 0.100; esophagus as long as 

 pharynx or shorter ; rectum short ; anus conspicuous, a short distance an- 

 terior to posterior end of body. Genital pore conspicuous, with radiating 

 muscles, slightly to the left, opposite base of pharynx. Testes large, tan- 

 dem, just posterior to midbody, transversely extended, close together, 

 with lateral edges bent dorsally and posterior borders deeply indented. 

 Posttesticular space about Yz body length. Seminal vesicle almost straight, 

 extending slightly posterior to acetabulum. Cirrus sac enclosing only the 

 cirrus and a few gland cells. Ovary immediately pretesticular, extended 

 transversely, 3-lobed. Vitellaria close together, from near anterior border 

 of acetabulum to near posterior end of body, filling posttesticular space, 

 not meeting posterior to anus. Metraterm muscular, extending to ace- 

 tabulum. Eggs 50 to 59 by 29 to 34 ^i, usually about 54 by 32 ix. Excre- 

 tory pore terminal or slightly dorsal. Excretory vesicle extending, dorsal 

 to testes, as far forward as ovary. 



