290 DR. n. LYSTBR JAMESON ON 



Species III. Tj/Iocejjlialum mimes. 



Eg-g, (?) hatching in^ 

 spa-water to become B,- 

 01- (?) swallowed by 

 ovster to become G. ^ 



(?) 

 A free-swimming larva, 

 like B above, onlj' 

 smaller. 



/ 



/ 



G 



Tlie smaller globular 

 cyst, TylocephaJum 

 minus, in connective 

 tissues of the Pearl- 

 Oyster. 



J^ / 



Au adult Ti/loce- 

 2)ltalum-\\\ie form, in 

 one of the oyster-eat- 

 ing Elasmobranchs. 

 Scolex probably about 

 •2 nun. in diameter. 



(5) Description of the two Globular Cestode Lart^ from 

 THE Ceylon Pearl-Oyster. 



I append the following descriptions. They are certainly 

 incomplete, being based on examination of preserved material 

 and on the descriptions of previous writers : — 



Tylocephalum ludificans, sp. n. (The larger globular larva ; the 

 supposed pearl-producing worm.) (PI. XLYI, figs. 58 (type) 

 & 59.) 

 The type, fig. 58, is in Slide 94 in Prof. Herdman's Collection. 



Tetrarhynchus unionifactor (young) Herdman. (For other figures 

 see Herdman's Report, Part II. Parasites of the Pearl-Oyster, 

 pi. i figs. 12 & 13 ; Part V. Pearl-Production, pi. ii. figs. 11,12, 

 & 176, pi. iii. figs. 1-5, 6, 7, 8, & 9 ; also Part Y. p. 21.) 



Globular Cestode larvfe, with rostrum or myzo7'hynchus (Linton) 

 retractile within a denticulated collar. Form more elongated 

 when hberated from capsule; length 0-5 to 1-5 mm. Average 

 diameter of seven specimens sectioned on Prof. Herdman's slides 

 and examined by the writer, 0*78 mm. 



