62 ILLINOIS BIOLOGICAL MONOGRAPHS [350 



In the above description it has been shown that this species differs from 

 the well-known C. truiicatus of Europe in a great many points, but in none so 

 radically as the following: The absence of chitinous hooks on the cuticula 

 of the lateral borders; the presence of radial muscles in the walls of the scolex, 

 and of a number of fine nerve commissures connecting the chief nerve strands 

 anteriorly instead of a single one; the vagina opening behind the uterus opening; 

 the absence of papillae and sphincter muscles surrounding the genital openings; 

 no enlargement of the vas deferens to form a seminal vesicle just before enter- 

 ing the cirrus-pouch; no connective tissue sac surrounding the whole of the 

 coiled vas deferens; the absence of dorsal retractor muscles of the cirrus-sac, 

 and the presence of the peculiar glands closely surrounding the pouch; no 

 "connective tissue and muscular sac" surrounding the beginning of the vagina; 

 the very different central connections of the genital ducts as regards the ovarian 

 isthmus ("ootyp" of Kraemer); and lastly, the absence of any such "shell- 

 gland" as described by the same author. Consequently it has been considered 

 to be specifically different from the European form and given a new name. 



The material studied consisted of three lots, Nos. 43, 165 and 382A of the 

 writer's colllection from the stomachs and intestines of several specimens of 

 Coregonus dupeifonnis (Mitchell) from Lakes Huron and Michigan as listed 

 above. 



BOTHRIMONUS Duvernov 1842, char, emend. 



Scolex with two surficial and almost spherical bothria whose forwardly 

 directed apertures may be separate or more or less completely fused to form 

 a single terminal opening, according to the degree of contraction of the ridge 

 separating the two internally, the latter representing the tip of the scolex 

 in other bothriocephahds. External segmentation completely absent. Female 

 genital cloaca with more or less well developed sphincter. Vitelline follicles 

 in the cortical parenchyma in two lateral fields. 



Occurence: In species of Acipenser and in teleosts. 



Type species: Bothrimonus sturionis Duvernoy. 



