7 -ON THE ANATOMY OF THYSANOCEPHALUM CRISPUM, LIN- 
TON, A PARASITE OF THE TIGER SHARK. 
By Edwin Linton, ni. d., 
Professor of Zoology in Washington and Jefferson College. 
I.— HISTORICAL. 
The first notice of this species was published in the author’s “ Notes 
on the Eutozoa of Marine Fishes of New England,” U. S. Fish Com- 
mission Keport for 1886, pages 461-468, plate ii, figs. 1 to 12. It was 
there described under the name Phyllobothrium thysanocephalum sp. 
nov. Subsequently it was discovered that it had been referred to the 
genus Phyllobothrium improperly. A new generic name was needed 
to accommodate it, and the species was therefore renamed as above in 
the author’s “ Notes on E ; oa, Part ii,” U. S. Fish Commission Keport 
for 1887, pot 1 ; ce of the change of name was given in a 
br< ; paper in the American Journal of Science 
Marc h, j.H89, page 240. The position to which the genus is assigned 
ocond paper is in the family Tetrabothriidce , subfamily Phila- 
canthince. 
II.— HABITAT AND DISTRIBUTION. 
This parasite has been found by the author thus far only in the tiger 
shark ( Galeocerdo maculatus), and there only on three occasions, viz, J uly 
23, 1885, August 3, and August 14, 1889, all at Wood’s Soil, Massachu- 
setts. In each case young, half-grown, and adult specimens were found 
together in the spiral valve, showing that the source of infection is 
distributed throughout a considerable portion of the year. In each 
instance, also, the parasites were numerous, and, in addition to the stro- 
biles, the chyle was teeming with free proglottides, which were con- 
tracting and elongating in the most active fashion, and achieving a 
kind of progressive motion by means of a sucker-like use of the hilum 
at the anterior end. 
The host, according to Jordan anil Gilbert, has a range from Cape 
Cod to the Indian Ocean. It would be too much, of course, to infer 
that the parasite is coextensive in geographical distribution with its 
host. This depends upon the range of individuals of the final host, 
and of the distribution of the intermediate host or hosts, rather than 
on the distribution of the species to which the host belongs. No mention 
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