Z PEOCEEDINGS OF THE NATIONAL MUSEUM vol. 81 



Class TREMATODA 



Family POLYSTOMIDAE van Beneden, 1858 



Genus POLYSTOMA Zeder, 1800 



Worms of this genus have long been known to be parasitic in North 

 American turtles, but Stunkard (1917) has suggested that they are 

 not cogeneric with Polystoina integerriinum^ the type species of the 

 genus. Ward (1917) erected for them a new subgenus, Polysto- 

 inoides. I have found four species of polystomes belonging to 

 Ward's subgenus, one of which appears to be new. 



POLYSTOMA (POLYSTOMOIDES) HASSALLI Goto, 1899 



This trematode has been found in the urinary bladder of Kino- 

 sternon subrubrum hippo(y)'epis and Chelydra serpentina in the vi- 

 cinity of Houston, Tex., and in the former species at Huntsville, Tex. 



POLYSTOMA (POLYSTOMOIDES) ORBICULARE Stunkard, 1916 



A polystome, which I assign to this species, was found in the blad- 

 der of several specimens of Pseudemys eUgans taken at Houston, Tex. 

 Some of the material exceeds in size the limits given by Stunkard 

 (1917) for Poly stoma orbiculare, but the relative size of the organs 

 remains constant, and there can be very little doubt that my material 

 is identical with Stunkard's. In respect to size, these larger speci- 

 mens resemble Polystoina inerme and P. spinulosv/rn MacCallum 

 (1918b) rather closely, but because my material shows many inter- 

 mediate types I believe that both species may prove to be synonymous 

 with P. orbiculare^ as Stunkard (1924) has already suggested. 



POLYSTOMA (POLYSTOMOIDES) TERRAPENIS, new species 



Plate 1, Figure 1 



Specific diagnosis. — Polystoina: Small polystomes of a flattened, 

 ovoid shape. The body length varies from 1.9 to 2.5 mm, and the 

 width varies from 0.72 to 0.82 mm. The caudal disk is circular, 

 from 0,64 to 0.8 mm in diameter, and the six suckers are nearly 

 equally spaced. The suckers are of the usual form, and in the 

 bottom of each there is a small hook. The suckers are 0.18 to 0.2 

 mm in diameter. Sometimes the larval hooks may be found on the 

 disk, but otherwise there are no hooks present. The larval hooks 

 are about 20/x long. The oral sucker is 0.26 to 0.28 mm long and 

 0.29 to 0.36 mm wide. It is followed inunediately by the pharynx, 

 which is 0.13 to 0.17 mm long and 0.19 to 0.22 mm wide. Even in 

 whole mounts a short esophagus may be distinguished. The in- 



