On Dissotreuia papillatum. "I k 



to him. Notwithstanding these points of resemblance affiliating 

 our new genus with the Paramphistomatldœ, there are others as 

 sharply differentiating it from any of the members of that family. 

 In the first place, the pretesticular position of the ovary is a 

 character which appears to occur in none of the Paramphistom- 

 atldœ, and only in Opisthodlscus dlplodlscoides, so far as I know, 

 do the testes lie not in front of the ovary but on the same level 

 and extend further backwards than the latter. Again, the 

 peculiar arrangement of the vitelline lobes appears to be a charac- 

 teristic of the new genus, as also the short and relatively wide 

 intestinal caeca extending but little into the posterior half of 

 the body. In view of these points of resemblance and difference 

 it appears to us that the question as to whether to refer the new 

 genus to a distinct family from the Paramphistomatldœ is more a 

 matter of convenience than of principle; but it is in our opinion 

 sufficiently different to justifiy the erection of a new family, which 

 is then to be called Dissotrematidœ and may be diagnosed as 

 follows: 



Fam. Dissotrematidœ. Digenea with more or less cylindrical 

 body; with oral sucker close to the front end, and acetabulum close 

 to the hind end, of the body; with long convoluted prepharynx and 

 well developed pharynx; ovary pretesticular; common genital aper- 

 ture ventral and median; no buccal pouches, no ventral pouch. 



Genus Dissotrema. Body sausage shaped, longitudinally con- 

 cave on the ventral side, convex on the dorsal, only slightly at- 

 tenuated at the front end, hind end well rounded; oral sucker 

 surrounded by lip-like prolongation of body; acetabulum subter- 

 minal, opening on the ventral surface by a longitudinal slit-like 

 aperture. Genital atrium present, opening in the ventral «median 

 line in the middle third of body; testes two, subglobular, 

 in oblique pair, in front of acetabulum; ovary subglobular, pre- 

 testicular; vitellaria continuous across the median line; the whole 

 genital organs with the exception of the vitellaria in posterior half 

 of body ; penis sac present. Prepharynx long, convoluted ; 

 pharynx very well developed; intestinal caeca short ; diges- 

 tive system almost entirely in front of genital pore. Excretory 

 vesicle elongated bottle-shaped, opening by its slender end close to 



