1 9 1 o- 1 9 1 1 . ] Trematodes Parasitic on British Fishes. 351 



small, and are each borne on little stalks at the end of a 

 narrow process which extends backwards from between the 

 two inflated suckers. The body of this species is narrowly- 

 ovate, soft, and flexible, and about half an inch in length, but 

 the length appears to be variable. A. merluccii has been found 

 on the gills of Hake (Merlucius merluccius Lin.) landed at the 

 Aberdeen Fish-Market. 



Sub-Fam. POLYSTOMATINiE. 



The only representative of this sub-family we have met 

 with is Ondiocotyle aip^endiculata (Kuhn), a parasite not un- 

 common on the gills of Skates and Dog-fishes. Professor 

 van Beneden describes these parasites as having a body of 

 extraordinary mobility, a mouth without lateral suckers, by 

 the body being bifurcated at the posterior end, and carrying 

 at a certain distance from the extremity six large fleshy 

 suckers supported by a stout plate. The posterior extremity 

 with the bifurcated apex is narrow and linguliform, and is 

 usually more or less reflexed upon the ventral aspect. This 

 species, which is not uncommon on the gills of large Thorn- 

 back and Grey Skates, varies in length from nine to about 

 twelve mm. 



Suh-Fam. Microcotylin^. 



The species belonging to this sub-family are readily re- 

 cognised by the extraordinary number of minute posterior 

 suckers with which they are provided. Those we have met 

 with represent the two genera Microcotyle and Axine. In 

 Microcotyle the body is narrow and elongate, and the suckers, 

 which are sessile or nearly so, are arranged at the posterior 

 end along the two lateral margins. In M. donavani van 

 Beneden & Hesse, found on the gills of the Ballan Wrasse 

 {Labrus lergylta) from the Moray Firth and other places, the 

 number of suckers in each of the two rows is thirty or slightly 

 over ; but in M. lahracis van Beneden & Hesse, found on 

 the gills of the Bass (Lahrax lupus) captured off the Lanca- 

 shire coast, the number of suckers is about double, the total 

 number being nearly one hundred and twenty. Both species 



