174 Papers from the Marine Biological Laboratory at Tortugas. 
mounted material does not show as many details of structure as could be 
desired. 
14. Phoreiobothrium lasium Linton. 
Report U. S. F. C., 1886, pp. 474-476, plate tv, figs. 24-29. Report U. S. F. C,, 
1887,. pp. 819-820. Proc. U.S. Nat.. Mus., voli xx, p. 447. BallsU. 8: 
F. C., 1899, pp. 272-273, 426, 427, 428. Bull. Bureau of Fisheries, vol. 
XXIV, Pp. 340, 343. 
One specimen was found in the spiral valve of the cub-shark (Car- 
charhinus platyodon), July 12. 
Dimensions, in life, in millimeters: Length 9.8; bothrium, length 0.50, 
breadth 0.20; breadth of head 0.42, of neck 0.16, narrowing to 0.12 at a 
distance of 0.35 from the head, then enlarging again; first distinct segment 
4.9 back of head, but indications of segments in front of this; first segment, 
length 0.35, breadth 0.22; last segment, length 0.84, breadth 0.36; length 
of longer prong of hook 0.10, of shorter prong 0.03. 
15. Thysanocephalum crispum Linton. 
Report U. S. F. C., 1886 (Phyllobothrium thysanocephalum), pp. 464-468, plate 
u, figs. I-12. Report U. S. F. C., 1887, pp. 823-824. Report U. S. F. C,, 
1888, pp. 543-556, plates LxI-Lxvul, figs. 1-43. Bull. U. S. F. C., 1890, pp. 
27, ot Year Book of Carnegie Institution of Washington for 1906, 
p. II10. 
Found in what was presumably a tiger-shark (Galeocerdo tigrinus). 
This shark was captured on June 2, before my arrival at the laboratory, 
and the spiral valve was preserved in formalin. While the shark had not 
been identified, the type of the spiral valve, the nature of the stomach con- 
tents, and, particularly, the presence of this entozoan in great numbers, 
both of large and small examples, all point to the tiger-shark as the host 
(see pp. 164, 167). 
These worms were found to be very numerous, large and small together, 
and still attached to the mucous membrane of the spiral valve. The folds of 
the pseudoscolex are preserved expanded and are in an unusually fine state 
of preservation. This condition is the result of the intestines having been 
placed in formalin while the worms were still adhering to the intestinal 
walls. Not only do the specimens exhibit the structure of the pseudoscolex 
better than would have been the case if the worms had been detached before 
they were placed in the preserving fluid, but they also illustrate the mode of 
attachment of this singular worm to its host. When this parasite attaches 
itself to the intestinal wall the minute head penetrates the mucous membrane 
while the fimbriated folds of the pseudoscolex are spread widely, thus making 
an adhering, and probably, at the same time, an absorbing organ. 
One of these scoleces was mounted in balsam. The diameter is 9 mm. 
There are eight pairs of primary divisions of the pseudoscolex. These 
are simply outgrowths of the anterior end of the strobile, being preceded 
