H. S. Pratt 
237 
situated between the anterior testis and the ovary as is the case of the 
other species of this genus (Looss, 1901), but he between the ovary and 
the dorsal body wall, and in case of greatly contracted individuals 
more or less in front of the ovary (Fig. 2). This is also true of much 
extended specimens, in which the ovary and the anterior testis are 
separated by a considerable distance: in these worms also these organs 
lie dorsal to the ovary. 
Looss (1901) has shown that the species of the genus Stephanochasmus 
fall naturally into several groups which he thinks form sub-genera and 
may possibly be equivalent to genera. One of these groups is repre¬ 
sented by Stephanochasmus cesticillus (Molin) and is distinguished by 
the greater width of the body behind than in front of the acetabulum, 
the extremely long cirrus sac and the ventral interruption of the oral 
spines. In another group, which is represented by S. minutus Looss, 
the hinder part of the body is also broad, the cirrus sac is relatively 
short and the oral spines are not interrupted ventrally. In the third 
group, which is represented by S. pristis, the body is not widened 
posteriorly, the cirrus sac is relatively short, the oral spines are not 
interrupted ventrally and the genital glands are separated from one 
another by -wide spaces. 
S. casus approaches nearest the second of these groups, being more 
closely allied to S. minutus than to any other species; It differs from 
it in being much larger, in having a relatively very long cirrus sac and 
in having yolk glands which extend forwards to the acetabulum. 
Linton (1910) has described a worm under the name of Lechradena 
edentula which I believe to be identical with S. casus. Its structure 
is the same in every detail except that it is without spines. Linton 
found but a single specimen of the species which had probably lost its 
spines as a result of a slight superficial maceration, a thing which might 
very easily happen. 
REFERENCES. 
Lintox, E. (1910). Helminth Fauna of the Dry Tortugas. n. Trematodes. Papers 
from the Marine Biological Laboratory at Tortugas. 
Looss, A. (1901). Ueber die Fasciolidengenera Stephanochasmus, Acanthocasmus 
und einige andere. Centralbl. f. Bakteriol. ParasitenJc. u. Infeldionslcr. 1 Abt. 
xxix, pp. 595, 628, 654, et seq. 
Sommer, F. (1880). Zur Anatomie des Leberegels, Distomum hepaticum L. 
Zeitschr. f. wiss. Zool. xxxrv, pp. 539-640, pis. 27-32. 
