42 ILLINOIS BIOLOGICAL MONOGRAPHS [260 



in the posterior end. In lateral extent they rarely traverse the outer 

 wall of the crura. The genital opening is located anterior to the pharynx. 

 The cirrus pouch extends to the anterior wall of the intestinal bifurcation. 

 The uterus fills out the entire space between the crura and its loops occa- 

 sionally span the outer wall of the same organ. The genital glands are 

 relatively small and occupy the positions so common to the species of this 

 genus. The posterior testis, not filling out the intestinal arch, is antero- 

 posteriorly flattened and measures 413 p. in width by 496 to 612 p in length. 

 The anterior testis is separated from the posterior by several uterine 

 loops and is smaller and spherical, measuring 331 to 413ju in diameter. 

 The spherical ovary is situated in a transverse plane anterior to and about 

 equally distant from the two testes. It is one-fourth smaller than the 

 testes measuring 215 to 331 p in diameter. The shell gland lies median 

 and posterior to the ovary, is spherical or only slightly ovoid and equal 

 in size to the latter organ. The receptaculum seminis although indis- 

 tinguishable in to to mounts is clearly seen in sections. It is anterior and 

 dorsal to the ovary. Wax reconstructions show it to be spherical and 

 approximately one-half the size of the ovary, measuring 150/* in diameter. 

 The ovarian complex is separated from the testes by uterine loops. The 

 eggs are thick shelled ovals, 66 /z wide by 115/z to 122 n long. 



Habitat: Abdominal cavity Host: Gallinago delicata (Ord.) 



Locality: ? Date: ? 



Collector: ? No. 08. 172 Ward collection. 



The relationships of this species is not so evident as it partakes of the 

 characteristics of a number of species. With respect to the lateral extent 

 of the uterine loops it is more nearly like Cyclocoelum mutabile and Cyclo- 

 coelum leidyi while in development of the vitellaria it simulates Cyclocoelum 

 halli. The pharynx and oral sucker are noticeably smaller than in any 

 known species of this genus and this is a feature of this species as is also 

 the small size of the genital glands and the proportionate size of the testes 

 to the ovary, a ratio of 4:3. 



CYCLOCOELUM OBSCURUM (Leidy) 



[Figures 8, 21] 



Syn: Monostomum obscurum Leidy 1887 



This species was described by Leidy as follows: "Elongated, elliptical, 

 flattened, obtusely angular in front, obtusely rounded behind, oral and 

 genital and other aperatures scarcely distinguishable. Length 4 to 8 lines; 

 width 1 line." 



"Numerous specimens in the stomach of a Jew-fish, Megalops thris- 

 soides" 



The host name Megalops thrissoides used for the Jew-fish by Leidy 

 1887 is evidently a lapsus calami. However this is corrected by Stiles and 

 Hassall (1894) to Stereolepis sp? 



