[265 NORTH AMERICAN MONOSTOMES 47 



this species by the larger pharynx, smaller sucker, the testes being equal 

 in size and also smaller in proportion to the size of the ovary. 



CYCLOCOELUM VICARIUM (Arnsdorff 1908) Kossack 1911 



Syn: Monostomum mcarium Arnsdorff 



The writer has not had opportunity to study specimens of this species 

 and hence must rely upon the descriptions of Arnsdorff (1908) and Kossack 

 (1911). Since the description of Kossack made after having studied the 

 original material is at variance with the original description only in minor 

 detail the writer has based the following description on the work of Arns- 

 dorff. 



Monostomes varying between 10.5 and 14.4 mm in length and 3 to 

 3.1 mm in maximum breadth. The body is opaque, flattened; ventral 

 surface flat, dorsal slightly swollen. The sidelines of the body diverge 

 from the small pointed anterior end to the height of the testes. From here 

 they form the bluntly rounded posterior end. The dorsal surface of the 

 body is quite wrinkled. These folds appear in optical section to form pap- 

 pillae. The mouth opening is terminal. The strongly muscular pharynx is 

 an elongate oval with a long diameter of 460 p and a breadth of 270/i. 

 The thickness of its wall is 130/*. The esophagus, 640 /A long, leads to the 

 intestinal crura which run parallel to the side walls of the body and anas- 

 tomose in the posterior end. The genital organs lie in the broad hinder 

 end. The posterior testis is flattened antero-posteriorly and measures 

 1190/z in length by 732 p in breadth. It lies in the middle line of the body 

 with its forward margin reaching to the vitelline duct. The anterior testi? 

 is spherical in form with a diameter of 835 to 878 p. It is removed anteriorly 

 from the posterior end and lies adjacent to the intestinal crura. The ovary 

 lies adjacent to the crural wall, opposite to the anterior testis and between 

 the positions of the testes. It is spherical and has a diameter of 402 /x. 

 Between it and the posterior testis is found the relatively small recep- 

 taculum seminis. 



The vitellaria are composed of numerous follicles which lie parallel to 

 the body wall and between that and the intestinal crura; they extend from 

 the region of the intestinal bifurcation to the posterior end where they are 

 separated by a short interval. The numerous transverse uterus loops 

 fill out the space between the crura and in the posterior half of the body 

 overlap them. The genital pore is situated just posterior to the pharynx. 

 The club-shaped cirrus pouch is small and does not reach the intestinal 

 bifurcation. The eggs are numerous, elliptical in form and measure 102 ./* in 

 length and 68 n in breadth. The ripe eggs hold a well developed embryo 

 as can be recognized by the black eye spots in the miracidium. 



