SEA-FISHERIES LABORATORY. 305 



from the top. There are four bothria present, though it 

 is usually very difficult to observe the boundaries of each. 

 The edges of these organs are deeply wrinkled and 

 crenulated. Even when a number of these cestodes are 

 killed in the same manner, the form of the scolices is often 

 extremely variable. The term " lettuce-like," however, 

 describes the general appearance very well. 



The measurements of the specimen figured are : — 



Greatest diameter of head : 3*5 mm. ; 



Length of strobila : 183 mm. ; 



Least width of proglottides (just behind the 

 neck) : 0'6 mm. 



Greatest width of proglottides : 2 mm. ; 



Greatest length of a proglottis : 1*75 mm. 

 The terminal proglottis is always the longest : it 

 generally tapers to a blunted posterior point. 



Phyllobothrium thridax, van Beneden. — Fig, 17. 



Hosts : Raia clavata, Carnarvon Bay and Bahama 

 Bank. 



I refer a number of smaller cestodes to this species 

 principally because of the difference in the general 

 appearance of the scolex and strobila. Neither in 

 Ph. lactuca nor in Ph. thridax is there any myzorhynchus, 

 and I have been unable to discover any trace of accessory 

 suckers in the former species. In the worms identified 

 as Ph. thridax there are, however, small accessory suckers 

 on the anterior borders of the bothria as shewn in van 

 Beneden's fig. 4, pi. 5 ("Vers Cestoides "). The appearance 

 of the bothria is very variable, but there is never the 

 highly complex folding which is to be observed in the 

 scolex of Ph. lactuca : the bothria can generally be seen 

 to be four in number, with comparatively simple outlines. 

 The strobilse in the specimens obtained were always 

 w 



