44 Papers from the Marine Biological Laboratory at Tortugas. 



sucker and also fill the body behind the testes to the caudal end. Excre- 

 tory vessel not made out clearly, but a spacious median vessel was noted 

 extending from the caudal end to the ventral sucker. The ova are char- 

 acteristically long and slender. The yolk-glands were not conspicuous, 

 the specimens evidently having been producing eggs for a long time.. 

 They are diffuse, marginal, and peripheral between the ventral sucker 

 and the anterior testis. Conspicuous nucleated cells form the inner layer 

 of the body-wall from about the level of the middle of the ventral sucker 

 to the posterior end. They are probably yolk-forming cells. 



Dimensions of specimen mounted in balsam: Length 4.55; breadth 

 0.86; oral sucker 0.53; pharynx 0.17; ventral sucker 0.38; ova 0.051 by 

 0.024 and 0.047 by 0.024 and 0.044 by 0.020. 



Host, Tenthis cceruleus: July 10, 1908, 1 fish, 2 distomes. 



General color orange-yellow. Dimensions of smaller specimen, life,, 

 flattened: Length 4.20; breadth 0.90; oral sucker 0.42; pharynx o.t6; 

 ventral sucker 0.23; ova 0.047 by 0.020. 



Stephanochasmus casus sp. nov. (Figs. 78-83.) 



Body linear to clavate, neck tapering; mouth surrounded by a 

 double row of spines, neck also spinose; all the spines are evanescent;: 

 ventral sucker 1.5 to 2 times the diameter of oral sucker; pharynx large, 

 usually pyriform, nearer ventral than oral sucker; prepharynx long, 

 esophagus very short ; rami of intestine extend to posterior end of body ; 

 genital aperture median at anterior border of ventral sucker; cirrus 

 spinose, cirrus-pouch long, slender, and cylindrical with the seminal 

 vesicle inclosed in its basal portion well behind the ventral sucker and 

 with the prostatic cells in its wall. Testes near posterior end close 

 together, one behind the other, on the median line; posterior testis, in 

 most cases oval and larger than the anterior, which is usually subglobu- 

 lar. Ovary subglobular, at anterior border of anterior testis. There is 

 a seminal receptacle in front of the ovary. The vitelline glands are diffuse 

 and fill the posterior and lateral regions of the body as far forward as 

 the ventral sucker. Out of 9 specimens the vitellaria of 6 extended a 

 little farther on the right than on the left side, reaching as far as the 

 middle of the length of the ventral sucker. The uterus lies between the 

 ovary and the base of the cirrus-pouch. The metraterm is beside and 

 dorsal to the elongated portion of the cirrus-pouch which it joins near 

 the genital aperture. The ova are large, and in the preserved specimens 

 are collapsed in a characteristic manner, with about 6 longitudinal fur- 

 rows, giving a ribbed appearance to them. In the specimens from 

 Neomcenis griseus and Ocyurus the ova in mounted material were from 

 0.061 to 0.065 i n length. In those from Neomcenis analis they ranged 

 from 0.075 to 0.085 in length. In those from Epinephelus they meas- 

 ured 0.078 in length. 



The specimens from Neomcenis analis were much larger than the 

 others, but they appear to agree with the smaller specimens from the 

 other hosts in all essential particulars. The spines around the mouth 

 and those of the neck were very poorly represented in all the distomes. 

 referred to this species. 



