76 Papers from the Marine Biological Laboratory at Tortiigas. 



so on opposite sides of the genital sucker; vitellaria mainly lateral and 

 dorsal in the anterior half of the body. The ovary is deeply lobed and 

 lies behind the testes. An oval body lying dorsally and in front of the 

 genital sucker may be a cirrus-pouch, but was too indistinctly seen to 

 be determined satisfactorily. The uterus fills the greater part of the 

 body and the very numerous ova conceal and obscure the other organs. 



Dimensions in balsam: Length 0.55 ; breadth 0.42 ; diameter of oral 

 sucker 0.24; pharynx 0.07; ventral (genital) sucker 0.07; ova 0.0 11 by 

 0.007. 



Host, Neomcenis griseus: July 5, 1906, 11 fish, few trematodes. 



Dimensions, life, flattened: Length 0.67; breadth 0.58; ova 0.020 

 byo.oi3(?). 



These trematodes bear a close superficial resemblance to Distomutn 

 monorchus Stoss. (Bull. Soc. Adr. Trieste, vol. xii, plate xv, fig. 62.) 



Metadena crassulata gen. et sp. nov. (Fig. 210.) 



Etymolgy: /^st^, among; dd^^, gland. 



The specimens here described when first seen were oval and rather 

 thick. They were killed over a flame under pressure. The following 

 description is based on a single very much flattened specimen. 



Body oval, covered with exceedingly minute, short, bristle-like- 

 spines; oral sucker relatively large; pharynx adjacent to oral sucker; 

 esophagus short ; intestinal rami extend to near the posterior end. Geni- 

 tal aperture on median line, a little in front of the middle of the length, 

 a little broader than long ; cirrus-pouch lies caudad and the large seminal 

 vesicles cephalad of the genital sucker. Testes two, oval, lateral, oppo- 

 site, their anterior borders about at the middle of the length of the body. 

 The ovary is many-lobed and situated in the middle of the body behind 

 the cirrus-pouch and between the testes. The vitelline glands are lateral 

 and extend from the level of the anterior edges of the testes to a point 

 about on a level with the seminal vesicle, or a little in front of it and nearly 

 opposite the bifurcation of the intestine; vitellaria also median between 

 the marginal lobes and the genital sucker and seminal vesicle. The 

 uterus is very voluminous and is filled with ova which obscure the other 

 organs. Excretory vessels not made out except to note that the excretory 

 pore is surrounded by radiating muscular fibers. 



Dimensions in balsam: Length 1.83; breadth 1.25; oral sucker, 

 length 0.42, breadth 0.39; pharynx 0.15; genital sucker, length 0.12, 

 breadth 0.15; ova 0.017 by 0.009. 



Host, Neonurnis analis: July i, 1908, i fish, 2 large and i small 

 trematode. 



Prodistomum gracile gen. et sp. nov. (Figs. 211, 212.) 



Etymology: Tipo, in sense of for, instead of. 



The specimens on which this description is based were in poor con- 

 dition and the anatomy could be only imperfectly made out. 



