116 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



instead, a number of cupules which may be either stalked 



or sessile. 



Phyllocotyle gumardi, van Beneden and Hesse. 



On the gills of the common gurnard, Trigla gur- 

 nardus, and yellow gurnard. A small species and easily 

 overlooked. Three pairs of sessile cupules. 

 Microcotyle labracis, van Beneden and Hesse. 



On the gills of the " bass," Labrax lupus. A 

 moderately large species with a number of sessile cupules, 

 but not common on any of the fishes examined by us. 

 Octobothrium scombri (Kuhn). 



On the gills of the common mackerel. A very slender 

 species and easily overlooked. Four pairs of sessile 

 cupules. 



Octobothrium merlangi (Kuhn). 



On the gills of the whiting. A large species of a dark 

 colour. Four pairs of cupules on short stalks. 



Dactylocotyle pollachii, van Beneden and Hesse. 



On the gills of the pollack. A large species of a 

 dark colour. Four pairs of cupules on moderately long 

 stalks. 



III. — Species with cupules, and a bifurcated median 

 appendage : — 



Onchocotyle appendiculata (Kuhn). 



On the gills of various Elasmobranch fishes (rays and 

 dogfishes), sometimes very common. Three pairs of large 

 cupules and a slender appendage, bifurcate at the apex. 



In addition to these Trematoda one representative of 

 the Hirudinea is known from the Irish Sea fishes. The 

 large skate leech, Pontobdella muricata, Leach, with its 

 corrugated, warty skin, is often found on rays captured 

 by the fisheries steamer. 



