A NEW CESTODE FROM THE MANEATER AND MACK- 

 EREL SHARKS. 



By Edwin Linton, 

 Of the University of Missouri, Columbia, Missouri. 



The present paper, Vv^hieh is a contribution from the United States 

 Bureau of Fisheries Laboratory at Woods Hole, Massachusetts, and 

 the Zoological Laboratory of the University of Missouri, Columbia, 

 Missouri, deals with a new parasitic Platyhelminth found in the 

 mackerel shark {I sums dehayi) and the maneater {Carcharodon 

 carcharias). It also discusses probable larval stages of the same. 



1. DESCRIPTION OF SPECIES. 

 PHYLLOBOTHRIUM TUMIDUM, new species. 



Type.—C^t. No. 7631, U.S.N.M. 



Scolex. — Bothria in pairs corresponding with the flat surfaces of 

 the strobile, apparently sessile in preserved specimens, but really at- 

 tached by very short pedicels, thin and leaf-like when extended, with 

 frilled or crumpled (lacinio-crispate) margins; each provided with a 

 conspicuous auxiliary sucker. Anterior end of scolex prolonged be- 

 yond the bothria forming an eminence which is dome-shaped in 

 outline in dorso-ventral, and conical, in marginal view. 



The bothria, as usually seen in preserved specimens, are contracted 

 into frilled and puckered folds to such a degree that their real nature 

 is difficult to interpret. A few were killed while still attached to the 

 mucous membrane of their host, and in them the real character of the 

 bothria is fairly well shown. Figures 2 and 3 are sketches of bothria 

 thus prepared. They are seen to be very thin and leaf-like structures. 

 That the bothria are not sessile, although appearing to be so, may be 

 demonstrated in scoleces which have been fixed under pressure. 

 Also, although the bothria are seated dorsoventrally in pairs, they 

 may appear, in front view, under pressure, to be cruciform. In sec- 

 tions the outer portion of the wall is seen to be a dense layer of 

 short muscle fibers lying at right angles to the surface. This layer 

 is of the same essential structure as that of the auxiliary suckers. The 



No. 2433— Proceedings U. S. National Museum. Vol. 61, Art. 12. 



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