17.3 



Tb YPA NORIITXCHA . 



Tetrarhynchus erinaceus, van Beneden. — Fig. 22. 



Hosts: Rain cJ avoid. R. inaciilafa, R. cirevlaru, 

 R. imcTocellata and R. hafis. 



Intermediate hosts : Pleuronectes platessa, Trigla 

 spp., Gadus morrhua, . G. aeglefinus and Merluccius 

 nih/aris. 



Pig. 22. Part of a proboscis of Tetrarhynchus erinacetis. 

 Mag. about 440 dia. 



This is one of the commonest tapeworms of Irish Sea 

 fishes; it enjoys a very wide distribution both in its adult 

 and pleurocercoid stages. T. erinaceus is always easily 

 recognised by the extraordinary hooks. Fig. 22 is a 

 view of a proboscis and shews the arrangement of the 

 hooks on one side of the organ. The larger curved hooks, 

 three of which can alw^ays be seen on one side, are about 

 005 mm. in length. Along one side of the proboscis is 

 a series of long, comparatively straight hooks which are 

 about 0"0-34 mm. long. The other hooks are short, 

 sti'aight or slightly curved and their average length 

 is about O'Ol'j mm. 



