SEA-FISHERIES LABORATORY. 115 



posterior sucker may be entire and circular in outline, or 

 divided into pairs of separate suckers. One genus has a 

 small secondary or " adhesive " disc attached to the large 

 one. These parasites live for some time after the death 

 of the fish and adhere very closely to the gills or skin, in 

 fact it is sometimes quite impossible to detach them with- 

 out injury. A very convenient way to remove them is 

 to leave the gills, or portions of the skin to which they are 

 attached, in fresh water for some hours ; this treatment 

 eventually kills the' parasite and at the same time causes 

 it to relax its hold. 



I. — Species with posterior sucker entire : — 

 Callicotyle kroyeri, Diesing. 



From the cloaca of Raia clavata. It is also found 

 on other rays, but always in the cloaca. The posterior 

 sucker has seven strong bands radiating from an inner 

 circle, the spaces between the rays are conical in outline 

 with the apices towards the centre. 



Phyllonella solece, van Beneden and Hesse. 



Attached to the scales on the " white side " of the 

 common sole. This trematode is of moderate size but 

 easily overlooked owing to the colour resembling that of 

 the fish. 



? Placunella pini, van Beneden and Hesse. 



This trematode which we identify as P. pini has only 

 been found on the gills of the yellow gurnard, Trigla 

 hirundo. It has eight distinct and two indistinct rays in 

 the posterior sucker. 



Deplectanum csquans, Diesing. 



Found on the gills of the " bass." A very small 

 species and sometimes abundant. 



II. — Species with no distinct posterior sucker, having 



