100 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[388 



Most of the specimens studied ranged in length from 50 to 240mm., but 

 none of them were considered to be complete posteriorly. The smallest 

 measured 28inm. in length and the largest 677mm. The scolex assumes a 

 variety of forms in preserved material, but agrees in general with the descriptions 

 of that of B. scorpii given by all the authors from the time of Rudolphi (1810: 

 51). Its commonest shape is shown in figures 21 and 22 where it is seen to 

 be quite elongated, somewhat broader and truncated anteriorly and narrow 

 posteriorly. The anterior portion is in reality in the form of a low pyramid, 

 comparable internally as well as externally with the terminal disc of the Tri- 

 aenophorinae. Its base is deeply indented dorsoventrally, that is opposite 

 the bothria, but rounded laterally. The whole scolex is broadest at about its 

 middle and narrowest at its posterior end. A portion of the latter is here con- 

 sidered to be the beginnings of the first segment on account of its being con- 

 stantly set off from the rest of the scolex ahead by a more or less definite groove. 

 The bothrivmi is in the form of an elongated V, being ordinarily widest and 

 deepest just behind the terminal disc and much narrower and shallower pos- 

 teriorly where it is not bounded by a definite wall but spreads out on the base 

 of the scolex. In many specimens, however, the scolex is so contracted and 

 the walls of the bothrium so protruded that the latter shows its greatest depth 

 at the middle of the scolex. In lateral view (Fig. 22) the scolex is more nearly 

 o\'al in outline since it is a little wider towards the base. From this fact it is 

 conceivable that MiiUer's (1788, Fig. 7) showing a more "orbicular" scolex 

 in B. scorpii in lateral view may be explained by supposing that he was dealing 

 with a much contracted specimen, altho in justice to the other side of the 

 question, it must be said that the first segments in his figure are by no means 

 contracted. It will be noticed that the figures of the scolex given here agree 



