NO. 14 manter: digenetic trematodes of fishes 



367 



Comparisons. The constant deep median cleft of the posterior margin 

 of each testis is one of the most distinguishing characters of this species. 

 Most species of Opecoelus have 3 pairs of labial processes. Opecoelus 

 mexicanus is very similar in foiTn of acetabulum, body form and size, and 

 egg size, but differs in that the 3 pairs of median labial processes are 

 longer; the vitellaria do not extend quite so far anterior; the genital pore 

 is opposite the middle of the pharjmx; the testes rather than being in- 

 dented medianly are extended at that point; the ovary is not so deeply 

 lobed, and the pharynx is longer in comparison w^ith its width. Opegaster 

 tamori has similar testes but no acetabular papillae and a more posterior 

 genital pore. 



Opecoelus inimici Yamaguti, 1934 

 (Plate 37, fig. 40) 



Host: Paralabrax nebulifer (Girard) 

 Location: Intestine 

 Locality: Cerros Island, Mexico 

 Number: Several 



These specimens seem to agree in all important specific characters 

 with Yamaguti's description of O. inimici, e.g. location of gonads, vitel- 

 laria, genital pore. Most measurements overlap those of the Japanese spe- 

 cies, although the eggs (54 to 63 by 27 to 34 i-i) are slightly smaller. 



It seems to the writer that O. sebastodis Yamaguti, 1934 is a synonym 

 of O. minor Yamaguti, 1934. Measurements of the two overlap. Yama- 

 guti separated the two on the character of the acetabular processes which 

 were 0.075 long in O. sebastodis as compared with 0.118 in O. minor. 

 But Yamaguti states (p. 347) that the 0.118 is the length when extended 

 and that "these appendages are variable in length according to contrac- 

 tion." Individual variation in the location of the opening of Laurer's ca- 

 nal is unknown. The vitellaria seem to reach somewhat more forward in 

 O. sebastodis, but this character is somewhat variable in my own collec- 

 tions of Opecoelus species. O. sebastodis is here considered a synonym of 

 O. minor. 



Opegaster acuta, new species 

 (Plate 37, fig. 41) 



Host: Abudefduf saxatalis (Linn.) 



Location: Intestine 



Locality: Socorro Island, Mexico 



Number: 12 specimens in one host, 9 in 3 others 



