NO. 14 MANTER : DIGENETIC TREMATODES OF FISHES 369 



Opegaster pentedactyla, new species 



(Plate 37, fig. 42) 



Host : Balistes verres Gilbert and Starks 



Location: Intestine 



Locality: Charles Island, Galapagos 



Number : 4 to numerous specimens in each of 2 hosts 



SPECIFIC DIAGNOSIS OF OPEGASTER PENTEDACTYLA 

 A contracted specimen measured 0.918 by 0.450; 3 more extended 

 specimens measured 1.360 to 1.424 by 0.337 to 0.450. Body widest at 

 acetabular level, tapering toward each end but more pointed at posterior 

 end. Forebody about %. total body length. Oral sucker 0.119 to 0.144 in 

 diameter; acetabulum not markedly protuberant, wider than long, 0.178 

 to 0.247 in transverse diameter, with transverse aperture. Sucker ratio 

 approximately 2:3. Acetabular lips each with 5 short papillalike inter- 

 locking tentacles. ( In the type specimen there seem to be only 4 tentacles 

 on the posterior lip, but the fifth might have been compressed by its an- 

 terior mate.) Prepharynx short; pharynx large, 0.087 to 0.110 in length 

 by 0.085 to 0.105 in width. It may be wider than long, longer than wide, 

 or of about equal dimensions. Esophagus shorter than pharynx in all 4 

 specimens. Possibly, when fully extended it might be as long as or even 

 slightly longer than the pharynx. Rectum short ; anus a short distance an- 

 terior to posterior end of body. Genital pore submedian, to the left, at 

 level of posterior end of pharynx. Cirrus extending to or almost to the end 

 of the esophagus ; cirrus sac, if present at all, very delicate and enclosing 

 only the cirrus; seminal vesicle with 2 curves, widening as it extends pos- 

 teriorly, reaching to posterior edge of acetabulum ; definite prostate gland 

 lacking but probably represented by a few isolated gland cells near semi- 

 nal vesicle opposite anterior edge of acetabulum. Testes ovoid, smooth or 

 with slightly irregular contour, tandem, intercecal, close together or, at 

 least, not far apart, in posterior half of body. A vas efferens arises dorsally 

 from near anterior end of each testis and unites with its mate to form a 

 short vas deferens near the seminal vesicle. The posttesticular space var- 

 ies from only 0.187 in the contracted specimen to 0.425. Ovary indis- 

 tinctly 3-lobed, heart shaped, the anterolateral lobes being more evident ; 

 shell gland dorsal at anterior border of ovary; seminal receptacle lacking; 

 Laurer's canal present; uterus preovarian, extending along the medial 

 side of the narrowed seminal vesicle, opening at the common genital pore 

 from the anterior side; eggs 46 to 50 by 26 to 29 /t; vitellaria extending 



