SEA-FISHERIES LABORATORY. 289 



Beneden, although the specimens obtained do not agree 

 very well with the description of this species. The worms 

 were small. The strobila was very easily broken up, and 

 in every specimen the most of the proglottides separated 

 from each other immediately the specimen was placed in 

 the preservative. PI. V., fig. 12, which has been drawn 

 from a preserved specimen, represents the head and neck 

 of one of these specimens. There are four botliria lying 

 very closely together. Each proboscis, when extended 

 fully, is about twice the length of a bothrium. The neck is 

 long and rather sharply marked off from the remainder of 

 the strobila by a constriction. The first proglottides are 

 very difficult to see, but are situated immediately behind 

 this constriction. The largest proglottis was about 2 to 

 3 mm. in breadth, and 3 to 4 mm. in length. 



The contractile bulbs are situated near the posterior 

 extremity of the neck. Each is about twice as long as it 

 is broad. 



The hooks are arranged transversely, or in very 

 imperfect spirals, on the proboscides. They have slightly 

 backwardly-recurved points, and their bases are expanded. 

 Each hook is in length about O'Olo mm. 



The following are the principal measurements : — 



Length of head... ... ... 0*6 mm. 



Breadth of head .. . ... ... 0*9 mm. 



Length of head and neck 



Length of contractile bulbs 



Breadth of contractile bulbs 



T. tetrabothrius of van Beneden is recorded from 



Mustelus and Acanthias. At least one other Tetrar- 



hynchid, T. lingualis, is also recorded from Acanthias, 



but the specimen described here is not this species. 



* Faune littorale Belgique ; Vers Cestoides. Nour Pleur. de l'Acad. 

 Roy. de Belgique, T. XXV., 1850. 



9-7 



ib mm. 

 0"4 mm. 

 0-22 mm. 



