38 ILLINOIS BIOLOGICAL MONOGRAPHS [256 



inner wall of the intestine and fills out entirely the space between the 

 crura. The eggs are thick shelled ovals, 51 to 66/x in width by 102/* in 

 length. 



Habitat: Lung Host: "Wild duck" 



Locality: Omaha, Nebr. Date: 1903 



Collector: C. E. Stringer No. 1041 Ward Collection 



This species is also found in the Leidy Collection vial no. 186 which has 

 been dried out and is in a poor state of preservation. John C. Johnson 

 collected this species from Fulica americana taken at Golden Gate Park, 

 San Francisco, Cal. in January 1919. 



Cyclocoelum pseudomicrostomum finds its nearest relative in Cyclocoe- 

 lum micro stomum (Crepl.). The two species are of nearly equal size. 

 The pharynx of the former is distinctly larger, the testes are not of equal 

 size as in C. microstomum and are slightly broader than long probably due 

 to pressure from the closely packed uterus. The ovary of Cyclocoelum 

 pseudomicrostomum is noticeably smaller than that of Cyclocoelum micro- 

 stomum, while the lateral extent of the uterus in the former species is more 

 restricted. With respect to the development of the vitelline glands 

 Cyclocoelum pseudomicrostomum presents the heaviest development found 

 in any known species of this genus. 



CYCLOCOELUM HALLI nov. spec. 

 [Figures 5, 11, 20, 36-42] 



Large monostomes varying in length from 11 to 14 mm in width by 3 

 to 4 mm in greatest width which is found slightly posterior to the middle 

 of the body. From this point the body tapers anteriorly to almost a 

 point and posteriorly only a little, forming an obtusely rounded end. 

 The body is muscular, dorsally convex, and ventrally fiat or slightly con- 

 cave. The body wall is entirely covered with numerous small pits ob- 

 served by Zeder (1803) in Monostoma mutabile. The subterminal mouth 

 leads by a funnel-shaped tube to the pharynx. This tube or mouth 

 proper is surrounded by a concentration of musculature which on the 

 outer margin is formed into circular bands, the outer covering of the sucker 

 (Figs. 36 to 42). The sucker is spherical in form and measures 387/x in 

 diameter. It is separated from the smaller (263 /z) but more heavily muscu- 

 lar, spherical pharynx, by the nerve commissure. The esophagus is 483 n 

 in length and extends from the posterior portion of the pharynx to the 

 dorsal side of the intestinal bifurcation. The latter a simple tubular struc- 

 ture lies along the margins of the body for its entire length and anasto- 

 moses at the posterior end. As previously described the excretory system 

 is composed of a system of tubules ramifying the entire body in this 

 species, as in Cyclocoelum elongatum. These tubules anastomose and 

 empty into the excretory bladder. In this species a single thin walled sac 



