DESCRIPTIONS OF FOUR DISTOMES. 37 



moderate length, oesophagus wanting; intestinal cseca extend nearly to the posterior 

 end of the body. Excretory vesicle Y-shaped, with a very long median portion and 

 short crura. Testes two, of large size, in the anterior portion of the posterior half of 

 the body, one diagonally behind the other. Ovary immediately behind the acetab- 

 ulum and in front of the testes; yolk-glands lateral, distributed in six to eleven 

 follicles on a side, extending nearly the length of the body; receptaculum seminis 

 present and very large; vesicula seminalis very long, enclosed in the cirrus-sac; 

 cirrus small. Genital pore at the posterior end of the pharynx. Egg measures 

 0.039 millimetre by 0.017 millimetre. Parasitic in the frog. 



The affinities of Ostiolum are with the genus Hsematolcechus, as described by 

 Looss ('94). It resembles that genus in the shape and size of the body of the 

 worm, the form and extent of the digestive tract, the form of the excretory vesicle, 

 the position of the testes, the position of the genital pore, the form and length of the 

 cirrus-sac and of the vesicula seminalis, the large size of the receptaculum seminis, 

 the absence of Laurer's canal, the form and distribution of the yolk-glands, the 

 great length of the uterus, the weakness "of the acetabulum, and the host which 

 harbors the animal. 



It differs principally from Hsematolcechus in the position of the acetabulum, 

 which is farther forward than in that genus, the size of the testes, which are much 

 smaller than in Hsematolcechus, in the arrangement of the uterine folds, which have a 

 general longitudinal direction in Hsematolcechus, and in the length of the excretory 

 vesicle, which extends much farther forward than in Hsematolcechus. In that genus, 

 also, the worms are often covered by spines, while in Ostiolum these structures did 

 not appear in any of the specimens examined by me. 



VI. BIBLIOGRAPHY. 



Leidy, J. 



'56. A Synopsis of Entozoa and some of their Ecto-congeners observed by the Author. Proc. Acad. Nat. 

 Sci. Philadelphia, vol. 8, pp. 42-58. 



Looss, A. 



'94. Die Distomen unserer Fische und Frosche. Bibl. Zool., Heft 16, 296 pp., 9 Taf. 



Looss, A. 



'99. Weitere Beitrage zur Kenntniss der Trematoden-Fauna Aegyptens. Zool. Jahrb. Abt. f. Syst., Bd. 12, 

 pp. 521-784, Taf. 24-32. 



Ltihe, M. 



:00. Ueber einige Distomen aus Schlangen und Eidechsen. Centralbl. f. Bakt. Parasit. u. Infek., Abt. 1, 

 Bd. 28, No. 17, pp. 555-566. 



Volz, W. 



'99. Beitrag zur Kenntniss der Schlangendistomeen. Arch, f . Naturg., Jahrg. 65, Bd. 1 , pp. 231-240, Taf. 20. 



