54 Papers from the Marine Biological Laboratory at Tortugas. 



section of the ovary shows the organ to be long oval, with its longer axis 

 transverse. Behind the ovary and contiguous with it is the relatively 

 large seminal receptacle, and ventrally on the right side of the ovary are 

 the lobes of the yolk-gland. This organ is deeply lobed, the lobes being 

 long clavate and apparently radiating from the right side. The ova are 

 very numerous, the entire body back of the ventral sucker being in large 

 part filled with them. They lie in dense masses behind the seminal recep- 

 tacle and between the ventral sucker and the ovary. The excretory 

 vessels could not be made out satisfactorily in the sections. 



Host, Teuthis cceruleus: Jiine 27, 1908, 2 distomes. 



These were associated with the species of Hysterolecitha rosea and 

 were not noted until after they had been sectioned. 



Dimensions: Length 2.55; breadth 0.45; oral sucker, length 0.28, 

 breadth 0.22; pharynx, length 0.13, breadth o.ii ; ventral sucker, length 

 0.32, breadth 0.28; ova 0.024 by 0.014, 



Opisthadena dimidia gen, et sp, nov. (Figs. 120-122.) 



Etymology: o-iadiix;^ hinder; Myj-j^ gland. 



Body rather slender, linear, compressed; ventral sucker three or 

 more times the diameter of the oral ; neck very short and conical ; phar3mx 

 subglobular adjacent to the oral sucker; esophagus ver}^ short, only 

 recognized in sections; intestinal rami extend to the posterior end. 

 Genital aperture between oral and ventral sucker on median line; cirrus 

 short and smooth; prostate large, elongated, along median line, dorsal, 

 behind ventral sucker, extending nearly to the middle of the length of the 

 body and followed closely by the seminal vesicle. Testes 2, one behind 

 the other and behind the middle of the body, oval, transverse. Ovary 

 situated a short distance behind the posterior testis, ovate, the longer 

 diameter transverse; yolk-glands 2, lying side by side immediately 

 behind the ovary; seminal receptacle dorsal to the ovary; shell-gland 

 behind the ovary and between the yolk-glands. The uterus begins be- 

 hind the yolk-glands where a few folds lie ; folds of the uterus in mature 

 specimens occupy the middle region of the body forward to the posterior 

 border of the ventral sucker, few between ovary and testis and between 

 the testes, but abundant in front of the testes. Anteriorly the metraterm 

 passes beside the prostate dorsal to the ventral sucker. It appears to 

 join the male genital duct a short distance from the genital aperture. 

 The ova are a little more than twice as long as broad. The excretory 

 vessel is single from the posterior end to a point a short distance behind 

 the ventral sucker. It there divides and the two lateral branches unite 

 above the oral sucker. 



A characteristic of this species is the very coarse muscle fibers 

 which lie in the body-wall. Coarse, longitudinal fibers also occur in the 

 intestinal walls. These intestinal muscles make their appearance near 

 the caudal border of the ventral sucker and continue to the posterior 

 end. They are strongest in the middle regions and grow somewhat 

 weaker toward the posterior end. 



