340 
Trematoilefi of Marine Fhhes 
likely to be materially increased except by the fortunate examination 
of some highly-infected fish such as a sun-fish or a sturgeon. A con¬ 
siderable addition to the number of monogenetic species may, however, 
confidently be expected. A small number of essentially British fishes 
may also prove to be the source of several additional digenetic records. 
Hitherto the most extensive account of the Trematodes of British 
marine fishes is that by Miss Lebour (1908), who deals with and 
describes about a quarter of the known forms. Her descriptions, with 
few exceptions, are accurate and reliable, while her illustrations give 
a correct impression of the parasites portrayed. 
Descriptions of the remaining species have to be sought in publica¬ 
tions which are, unfortunately, not always readily accessible. It 
would be well if these scattered observations could be brought together 
in one publication, and it is hoped that the present paper may serve 
as a nucleus for such a complete and inclusive account. 
I have attempted to compile a list of all the British marine fishes 
from which Trematodes have been recorded in this country, together 
with a supplementary list of the parasites which have been recorded 
from British fishes outside the British area, and which have not as yet 
been recorded from British waters. The latter list is, unfortunately, 
not quite complete, as several papers bearing on the subject could not 
be consulted. It is hoped, however, that these lists will be of value 
for reference to workers who may take up a more extended investigation 
of the subject in the future. It is evident from the last list that a certain 
number of gaps may yet have to be filled in the British records. The 
majority of the observations in that list have been made in the Mediter¬ 
ranean, chiefly by Kudolphi, Monticelli, Stossich, Looss and Odhner. 
A considerable number owe their origin to P. J. van Beneden on the 
Belgian coast, while Olsson and Odhner are responsible for a large 
number of records from northern fishes. 
On comparing these twm lists some interesting points are brought 
to light. In the first place there are eight more species of fishes 
tabulated in the first list than in the second. This is due to the fact 
that 27 species appear in the first list and not in the second, whereas 
only 19 appear in the second and not in the first. In the first case 
the explanation may be one of three: that the total cpiota of parasites 
has been found in the British area, or that the fish have not been 
thoroughly examined in other localities, or that the parasites of these 
fish do not occur outside British waters. In the second the interpreta¬ 
tion is the reverse, namely that the fish have not been thoroughly 
