159 



pair is united at the bases. They project considerably 

 from the margin of the head and are very conspicuous. 

 The shapes of the proglottides vary from region to 

 region of the strobila and give the worm a unique appear- 

 ance. There is no neck and the proglottides immediately 

 posterior to the head are each provided with four laciniate 

 lobes or lappets. A section of the M-orm is given in fig. If 

 A, and shows the situation of these lobes. A litle way 

 further back (fig. 14 B) an additional rounded lobe appears 

 at the middle of the posterior margin of each proglottis, 

 and these median lobes characterise the region of the 

 strobila about one-third of the distance between head and 

 extremity. Further back than this (fig. 14 C) this 

 median lobe sub-divides into two, and further back yet 

 these subsidiar}^ lobes disappear and the posterior margin 

 of the proglottides shew only a blunt rounded prominence 

 at each lateral and posterior corner. Towards the posterior 

 extremity of the strobila the proglottides lengthen out 

 greatly until they are about thrice as long as they are 

 broad, and the terminal proglottis is always pointed. 

 The whole strobila withstands preservation in formalin 

 very well and does not break up on immersion in this 

 fluid. 



Phyllobothriid.e. 



Phyllobothrium lactuca, van Beneden. — Fig. 15. 



Hosts: Raia clavata, Carnarvon Bay; R. circularis, 

 Beaumaris Bay; R. hatis, off-shore grounds. 



This worm, which is usually ver}- commonly present 

 in the intestines of various rays, is easily recognised by 

 the extraordinary shape of the head and by the appearance 

 and length of the strobila. P. J. van Beneden's figure of 

 this species in the " Recherches sur les vers Cestoides " 

 (also in Broun, Taf. XLL, fig. 10 j, is drawn trom a 



