SEA-FISHERIES LABORATORY. 



317 



TRYP ANORH YNCH A . 



Tetrarhynchus erinaceus, van Beneden. — Fig. 22. 



Hosts : Raia clavata, R. maculata, R. circularis, 

 R. microcellata and R. hatis. 



Intermediate hosts : Pleuronectes platessa, Trigla 

 spp., Gachis morrhva, G. aeglefinus and Merluccius 

 vulgaris. 



Fig. 22. Part of a proboscis of Tetrarhynchus erinaceus. 

 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 always 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"034 mm. long. The other hooks are short, 

 straight or slightly curved and their average length 

 is about O'OIB mm. 



