290 DR, H. LYSTER JAMESON ON 
Species ILL. Tylocephalum minus. 
B’ 
(?) 
A free-swimming larva, 
hike B above, only 
smaller, 
N 
A” : : 
ae. The smaller globular 
Joo ( é Yin es 
Egg, (?) hatching in cyst, Tylocephalum 
sea-water to become B,——_— == ia minus, in connective 
or (2) swallowed by tissues of the Pearl- 
oyster to become G. —\ Oyster. 
X ¥ 
A 
An adult = Tyloce- 
phalum-like form, in 
one of the oyster-eat- 
ing _ Elasmobranchs. 
Scolex probably about 
‘2 mm. in diameter. 
(5) Descrierion OF THE TWO GLOBULAR CEsTopE LARV# FROM 
THE CEYLON PEARL-OYSTER. 
IT 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. XLVI. 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 I]. Parasites of the Pearl- Oyster, 
pl. i. figs. 12 & 13; Part V. Pearl-Production, pl. 11. figs. fat ote 
& 176, pl. ii. figs. 1-5, 6, 7, 8, & 9; also Part V. p. 21.) 
Globular Cestode larvee, with rostrum or myzorhynchus (Linton) 
retractile within a denticulated collar. Form more elongated 
when liberated from capsule; length 0°5 tol‘) mm. Average 
diameter of seven specimens sectioned on Prof. Herdman’s slides 
and examined by the writer, 0°78 mm. 
[32] 
