578 
Cestodes from Selachians 
8. Galliobothrium convolutum n. sp. 
(PI. XXIII, figs. 14^—19 and Text-fig. 2.) 
This species is very commonly found in the spiral valve of Cynias 
manazo (Bleeker) in Japan. The specimens which I examined were 
obtained from the shark, chiefly on three occasions, viz., 24. and 27. 
iv., and 9. v. 1907, in Tokyo. I have frequently found them associated 
with other species of cestodes, some of which I have already described. 
External characters. Total length 55—110 mm. Head sub¬ 
quadrate and provided with four bothridia; its length and breadth 
vary naturally according to the state of contraction, on an average 
it measures ca. 1-0 x 0-7—0-8 mm. 
In my largest specimens, the head measures 1-5 x 1-0^—1-2 mm. 
The bothridium is elongated oval in shape, measuring 0-6—0-7 x 
0-3—0-35 mm. Each bothridium turns outward hut not forward, 
and its face is divided into three loculi by two transverse costae, the 
anterior costa lying in the middle or a little posterior to the middle 
of the bothridium ; the second costa near the posterior end. Therefore, 
the anterior loculus is the largest and the posterior the smallest. The 
wall of the bothridium is somewhat thickened. Each bothridium 
bears one pair of thorn-like simple dark brown hooks (PI. XXIII, fig. 15), 
the one being much larger than the other; the larger hook measures 
0-3 X 0-1 mm. (basal width), and the smaller 0-17 x 0-06 mm. The 
paired hooks are closely apposed basally. Each hook is accompanied 
by a small process situated externally to its base and embedded in 
the tissue so as to be invisible from exterior. 
In front of the hooks each bothridium is surmounted by a sub- 
triangular pad, bearing a small accessory sucker anteriorly. The head 
is separated from the rest of body by a distinct neck, which may measure 
2 X 0-5—0-7 mm., but its shape varies greatly in life. 
In the strobila the breadth of the segment is always greater than 
its length; the breadth gradually increasing toward the middle of the 
body where it may reach a maximum along a succession of segments 
after which the breadth again diminishes shghtly toward the posterior 
end. The length of the segments increases gradually and continuously 
from anterior to posterior end of t^e strobila. Actual measurements 
of length and breadth are slightly variable according to the different 
individuals or to the condition even in the same individual, but in the 
latter case there is no remarkable variability. Sometimes, though very 
rarely, we may find that the length is greater than the breadth in the 
