566 
Cestodes from Selachians 
field respectively and the inner ends are continuous with one another 
before the shell gland, forming a small isthmus. In cross sections 
through the level of an isthmus, the arrangement of ovarian laminae 
resembles an H, with the four limbs thickened, the horizontal part 
being very short or entirely obliterated. Each lamina, moreover, is 
indented superficially and irregularly into a number of rounded lobes. 
The oviduct arises at the middle part of the isthmus, where it forms 
the “egg-swallowing apparatus”^ of German authors; thence it runs 
backward along the vagina to unite with it at some distance from the 
shell gland. The common duct leads forward into the shell gland. 
The structure of the oviduct is similar to that of the vagina. 
It is not an e^sy task to find the complicated connections of varibus 
parts of the female organs. Thev are diagrammatically shown in 
PI. XXIII, fig. 5. 
3. Orygmatobothrium velamentum n.sp. 
(PI. XXIII, figs. 6—11.) 
The material was obtained from the spiral valve of Cynias manazo 
(Bleeker) on 10. v. 1911, in Hiroshima. The specimens were numerous 
and associated with other Cestodes such as P. lactuca (already referred 
to). Most of them are fully grown and mature, but I have not found 
gravid segments in any specimens. 
External characters. The mature form measures 30—40 mm., 
besides which there are some smaller young-stage specimens. The 
head (PI. XXIII, fig. 6) is provided with four cup-like bothridia, disposed 
crosswise and provided either with very short peduncles or nearly 
sessile. The bothridia are directed forward and slightly outward, 
their anterior subcircular surfaces being nearly at right angles to the 
long axis of the head; each bothridium bears two small accessory 
suckers of nearly the same diameter, one at the anterior angle, the 
other central; the anterior sucker is more easily visible than the central 
one, but by the contraction of the anterior portion of the bothridium, 
it is often hard to detect; the central sucker is weakly developed and 
at times difficult to see. This obliteration of the accessory suckers 
is frequent, and when I first studied the Cestode I falsely concluded 
that they were absent and that I was dealing with a member of the 
genus Anthobothrium, but the subsequent examination of many good 
specimens revealed my error. The border of the central accessory 
^ Hereafter called “egg-swallower.” 
