828 DR. W. A. CUNNINGTON ON PARASITIC 
well marked, simple or slightly bilobed ; terminal portion of body 
not upturned. 
Total length of specimen, 10-0 mm. 
From tip to tip of dorsal cephalic arms, 4-2 mm. 
Remarks.—It is unfortunate that this species has to be 
described from a single specimen. Although no egg-sacs are 
present, it isalmost certainly adult, and there seems no reasonable 
doubt that it represents a distinct form. This unique individual 
has unluckily been badly preserved, and as a result the body 
is nearly flattened towards its posterior end. It thus becomes 
impossible to determine the real diameter of this part of the 
body, and so to express the amount of dilatation which it has 
undergone. Similarly, an artificial twist in the body makes it 
virtually impossible to state the nature and degree of torsion, 
From the shape of the cephalic arms, this form may be placed 
not far from the oldest known European species, L. eyprinacea 
and Z. esocina, from which it is nevertheless perfectly distin- 
guishable. ‘The dorsal cephalic arms in this specimen, as will be 
seen from fig. 9, are not quite bilaterally symmetrical, a condition 
of things which is met with in the genus from time to time. 
Occurrence.—The specimen belongs to the collection of the 
British Museum. Particulars are given as follows :—‘ From 
Barbus bynni, bought in Old Cairo fish bazaar—caught in the 
Nile, Loat Coll., no. 26.” 
3. General Remarks. 
It is clear that, whatever may be the case for marine fishes, 
the fishes of fresh water are relatively seldom the prey of parasitic 
Eucopepoda under natural conditions. This is indicated by the 
paucity of material in the collections under review, for the 
specimens on which this paper is based come from eight indi- 
viduals only. On the Third Tanganyika Expedition, of which 
I can speak personally, very large numbers of fish were examined, 
on only two of which were such parasites discovered. It is 
instructive to compare with this the occasions on which Argu- 
lidee—also external parasites—were obtained. They were taken 
18 times in Lake Tanganyika, and in some cases on two or three 
individuals of the same species at the same time, while with 
lesser opportunities, they were found on three separate fish in 
the Victoria Nyanza, as against no record at all of parasitic 
Euecopepods. A study of the literature of the subject confirms 
our conclusion. ‘There are, it is true, other families besides the 
Lerneeide which are represented in fresh water, but they do not 
constitute a very formidable assemblage, while the genus Lerne- 
ocera, sole representative of its family, contains but a small 
number of species. Of these species it is certainly true to say 
that they are not very common, and in the majority of cases the 
remark is equally true of the other parasitic forms. When 
natural limits are transgressed, as they usually are in the stocking 
of ponds and rivers with fish, there not infrequently occur 
