1910-1911.] Treniatodes Parasitic on British Fishes. 3 49 



than G, Kroyeri, and is of a somewhat different shape. The 

 posterior sucker is transversely broadly ovate, the width ex- 

 ceeding the length by about one-fifth ; it has seven sub- 

 marginal compartments and a central one, as in C. Kroyeriy 

 but the centre compartment, instead of being round, is trans- 

 versely narrow. There do not appear to be any suckers at 

 the anterior end. Length about nine mm. The third species, 

 Heterocotyle pastinacce T. Scott was found on the gills of 

 the Sting Eay {Trygon jpastinaca), captured in the Dornoch 

 Firth in October 1903. The large posterior sucker in this 

 species is oval-shaped, the width being greater than the 

 length; the under surface is divided into eight compart- 

 ments, but the one on each side is about tvdce as large 

 as any of the others, and there is also a small diamond- 

 shaped space in the centre. The species is very small, 

 measuring scarcely one and a half mm. in length. 



Suh'Fam. Udonellin^. 



The only representative of this sub-family with which I 

 am familiar is the Udonella caligorum of Johnston, a species 

 sometimes common on Caligus curtus 0. F. Mtiller, which in 

 its turn is frequent as a parasite on codfishes and other 

 Gadoids. 



Fam. POLYSTOMATID^. 



Suh'Fam. OCTOBOTHRIINiE (syn. OCTOCOTYLINiE).^ 



The species arranged under the Polystomatidse are provided 

 with several posterior suckers, and they have generally two 

 in front. In Octobothriinse the number of posterior suckers 

 is eight, and though their arrangement differs considerably 

 in the different genera belonging to this sub-family, their 

 number remains fairly constant. Species representing six 

 genera of the Octobothriinse have been found on British 

 fishes. They include Octobothrium — the premier genus — 

 PterocotyUy Dactylocotyle, Phyllocotyle, Plectanocotyle, and 



^ As the generic name Octocotyle has been set aside in favour of Octobothrium ^ 

 the sub-family name must be correspondingly modified, especially as Octobothriv/m 

 is the older genus. 



