638 DAVID HILT TENNENT. 
Distomum gracilescens, Rud. (Synopsis, p. 409), from 
Lophius piscatorius. (Gasterostomum rather than Dis- 
tomum because the mouth is situated in the ventral sucking 
disc.) 
In 1857 Wagener (8) gave figures of an old and two young 
specimens of G. fimbriatum. 
Wedl (4, 1857) redescribed and figured Distoma cam- 
panula, Dujardin (‘ Histoire naturelle des Helminthes,’ p. 
435), from intestinal slime of Esox. 
Wagener (5, 1858) recognised the identity of this form 
with G. fimbriatum, v. Siebold. 
In this paper (1858) he again discusses the three species 
then known. 
1, G. minimum, Wagener, from intestine Trigle micro- 
lipidote. 
2. G. gracilescens, Wagener, from intestine Lophii 
piscatorii= Distoma gracilescens, Rud. 
3. G. fimbriatum, v. Siebold = Distoma campanula, 
Dujardin, from intestine Esocis lucii, Perce fluviatilis, 
Lucioperce Sandre; encysted forms on gills of Cyprinus, 
showing the points in which they agree, and calling attention 
to the fact that the first two are from the Mediterranean 
where B. haimeanus is found, while the last is a fresh-water 
form, as is B. polymorphus. 
As a means of distinguishing the species he proposes 
making use of the difference in the direction of the gut, and 
the relative size of the sucking disc, and of the eggs. 
Diesing (6, 1858) in a systematic paper separates the three 
forms above mentioned, retaining the genus Gasterostomum 
for the species fimbriatum, and creating a new genus, Rhipi- 
docotyle, for the species gracilescens and minimum. 
1. Rhipidocotyle gracilescens= Distoma graci- 
lescens, Rud. =G. gracilescens, Wag. 
2. R. minimum=G. minimum. Wag. 
The complex and peculiar structure of the anterior end of 
G. fimbriatum, which was described by Wagener (1857), 
