40 ILLINOIS BIOLOGICAL MONOGRAPHS [320 



pass from the base of each sucker to each of the other suckers. Many 

 of the muscles branch and ramify thru the tissue of the disc. 



The anterior sucker is 0.2 mm. long and 0.42 mm. wide ; the pharynx 

 is 0.37 mm. long and 0.4 mm. in width. No esophagus is visible in the 

 single toto preparation and only the anterior part of the intestine can 

 be seen. 



The testis is slightly anterior to the middle of the body; it is oval, 

 0.36 mm. in length and 0.42 mm. in width. The sperm duct can be 

 traced dorsally and anteriorly; cephalad of the ovary it expands into 

 a seminal vesicle which stains deeply due to the presence of spermatozoa. 

 The genital coronet contains thirty-two hooks, equal in size and similar 

 in shape. 



The ovary is on the left side of the body, about midway between 

 the testis and the genital pore. The oviduct arises at the median pos- 

 terior margin and passes mediad, but the structure of the ootype could 

 not be made out. The uterus can be distinguished at the level of the 

 ovary on the opposite side of the body and is empty. Laterally the 

 vaginae are visible and the vitello-vaginal canals can be traced mediad 

 a short distance from the ceca. The vitellaria are strongly developed, 

 anteriorly they extend to the middle of the pharynx, and posteriorly 

 to the caudal disc. There is a strand of follicles across the body from 

 side to side between the pharynx and the level of the genital pore. The 

 follicles occupy the dorsal and lateral regions of the body but anteriorly 

 are reduced in the median area and are absent in the fields over the 

 testis and ovary. They obscure the ceca caudal to the testis. No vitel- 

 line ducts were seen. 



The excretory vesicles appear one on either side of the body dor- 

 sally, at the level of the bifurcation of the intestine. 



In number of genital hooks this specimen agrees only with P. coro- 

 natum Leidy. A comparison with a type specimen of P. coronatum 

 shows that in the latter form the pharynx and testis are much smaller 

 and the suckers of the caudal disc are much larger. 



POLYSTOMA CORONATUM Leidy 1888 

 [Figure 27] 



This description was made from a single type specimen from the 

 United States National Museum. The worm was stained and mounted 

 in toto. 



Leidy (1888) says the host is the common food terrapin, and the 

 previous year, speaking of eating terrapin, he mentions Emys palustris 

 and Emys rugosa. Braun (1879-1893) lists the species from Cistudo 



