NO. 14 MANTER : DIGENETIC TREMATODES OF FISHES 351 



testinal bifurcation a short distance anterior to acetabulum; ceca extend- 

 ing to near posterior end of body. 



Genital pore a long, diagonal slit near left anterior edge of acetabu- 

 lum, its aperture approximately same length as aperture of acetabulum. 

 Testes smooth, tandem, intercecal, posterior to midbody, longer than 

 wide, close together. Postesticular space 0.337 to 0.570, or about Yq 

 body length. Cirrus sac curved, claviform, extending to or usually slightly 

 beyond posterior edge of acetabulum ; external and internal seminal vesi- 

 cles present, the latter usually inconspicuous ; pars prostatica large ; cirrus 

 thick walled. Genital atrium large with thick more or less folded walls 

 continuous with a short, thick-walled metraterm. Ovary globular, medi- 

 an, separated from anterior testis by the large spherical seminal recep- 

 tacle ; Laurer's canal present ; gland cells around uterus at base of metra- 

 term ; vitellaria from posterior edge of acetabulum backward, surround- 

 ing ceca, confluent posterior to testes ; eggs 60 to 68 by 34 to 54 /a, usually 

 about 66 by 36 /x. 



Excretory vesicle a narrow sinuous tube extending forward to poste- 

 rior end of pharynx, receiving near its posterior end 2 pairs of small col- 

 lecting tubules. 



Discussion. The peculiar pharyngeal processes of this trematode seem 

 to be unique. Specimens of Opechona gracilis (Manter) show very slight 

 elevations of the anterior edge of the pharynx which suggest rudiments of 

 such structures. These pharyngeal processes are very distinctly from the 

 tissues of the pharynx but are not comparable to the lobed border of the 

 pharynx in some trematodes (Megapera, Thysanopharynx). 



Not mentioned in the above diagnosis are thin- walled tubes in the 

 forebody similar to or possibly lymph vessels. Their number was not de- 

 termined because of their winding, convoluted nature. One pair seems to 

 extend near the lateral sides of the body, another pair along the sides of 

 the prepharynx. None were seen posterior to the acetabulum. 



Opechona pharyngodactyla differs from all other species in the genus 

 in its pharyngeal processes. In extent of vitellaria it is like Pharyngora re- 

 tractilis Lebour [considered by Nicoll to be a synonym of O. bacillaris 

 (Molin)], O. i'com^ri Yamaguti, and O. orientalis (Layman). It differs 

 from all species, except possibly O. scombri, in the fact that the pharynx 

 is always longer than the esophagus and pseudoesophagus combined. Its 

 eggs are larger than those of O. scombri or O. orientalis. Its ovary is not 

 trilobed as in O. orientalis. 



